The emergence of the curatorial as a concept since the 1990s may be considered a part of an attempt to define the field of curatorial-cultural praxis in its broadest sense. In turn, this development may be situated in relation to the concomitant, nevertheless debated, expansion of curating within the cultural field. Curatorial work no longer concerns solely the display of artworks and the task of exhibition-making; it is now also understood as a practice centered on longer-term, less object-orientated, discursive-educational projects that involve various people as instigators and actors (~discursivity ~collaboration ~participation ~educational turn ~performativity). Subsequently, curatorial work—which may also be read as a reaction to authorial and consolidated forms of exhibition production—has become more conceptual, increasingly concerned with process- knowledge- and research-based endeavors. Likewise, expanded curatorial work enters into social and political discourses, inasmuch as many projects—with their thematics, research or statement—wish to contribute to socio-political realities, to understand or even change parts of the world around us (~collaboration ~participation).
The concept of the curatorial can also be linked to those inquiries, which attempt to make a distinction between the manifestation of an act in practice, and its broader yet more elusive conceptual framework. The differentiation of politics vs. the political by Chantal Mouffe  or that of critique/criticism vs. criticality by Irit Rogoff  are cases in point. The newly coined (latter) concepts of these distinctions are frequently put forth as a desired direction to follow. In terms of curatorial practice, this distinction is made between curating (under which mostly exhibition-making is understood) and the curatorial; nevertheless, with the latter concept, the emphasis is on the relation of curating and the curatorial, not their difference.
The conceptualizations of the curatorial in the contemporary art field are manifold; proponents of this notion have varied interpretations as to its meaning, significance, and modus operandi. Among others, it has been understood as something more than curating, as a form of critical thought that may be deferred in its manifestation;  an expanded function of mediation that aims to question and critique the status quo;  or a dynamic constellation of activities with ways of co-productively and dialogically working with others, which, at the same time, is able to disrupt consolidated forms of practice.  However, as a common denominator, the curatorial may be best understood broadly, as a way of working within the cultural field. Correlatively, this notion can be viewed to attempt to posit curatorial work as a discipline as well as a socio-cultural practice for generating, contextualizing and making art and ideas public. One is reminded here of Annie Fletcher’s remark in relation to Paraeducation Department, in a 2005-interview, which can be regarded to delineate the notion of the curatorial:
“The mechanism of an exhibition is simply not enough to describe what goes on in art, or what goes on at the practice level. What we used to articulate in terms of particular artists oeuvres, or curatorial oeuvres I suppose, should be democratised. That is what Paraeducation was about. I hope that everybody grasps the method – it’s not an artwork, but just a method of working.” 
The curatorial as a methodology, however, cannot be ascribed to a specific set of practices or projects; its outcome can be a discussion, an exhibition, a space, a book, an action, a combination of all these or other, often intermediary forms. Yet, one of the salient features of the curatorial, in terms of the people involved, may be its collaborative and collective character (~collaboration ~participation discursivity ~educational turn) Working together curatorially could mean several individuals coming together, sharing responsibility for a project to realize, a trust in one another’s work within that, as well as potentially realizing a (plat)form that involves (many) others in a formative way. Consequently, these kinds of projects tend to be polymorphous; they are longer-term, complex, and often research-based, with many levels and instances of realization, in a stage of perpetual becoming, This reminds us, in relation to this ever-becoming position, of Irit Rogoff’s Derridaesque positioning of the curatorial within the gap (or différance) between a project’s proposition and its inability to carry out that very proposition.  Although locating the workings of the curatorial in the negative hypothetical might be a bridge too far, the "impossibility" of curatorial work is a familiar situation to many, as it is often the case that there is a gap between the intention of an exhibition or project and its (physical/concrete) realization. 
It is also important to note that the concept of the curatorial is not embraced by the whole curatorial-contemporary art field as such. The dividing line between the opponents and proponents seem to be a hierarchized and oppositional understating between exhibitions-making and discursive practices, as well as between artists and curators (~discursivity). Jens Hoffmann is one of the most outspoken critics curatorial practices that do not concern exhibition-making. With coining the term paracuratorial, which could be regarded as a (close) synonym for the curatorial, Hoffmann criticizes curatorial practices that go beyond exhibition making.  The para is derived from Gérard Genette’s paratext which are all the elements beyond the body text of a book (blurb, back matter, typography, etc.). Hence, the paracuratorial, in Hoffmann’s sense, is all the activities which are either outside of exhibition making (such as lectures, screenings), yet posited as the outcome of curatorial work (~discursivity ~educational turn), or which are, as he states, “exhibitions without art, working with artists on projects without ever producing anything that could be exhibited”  (~performativity).
Beyond the debate about the centrality of the exhibition form, another criticism leveled against the curatorial is that it prioritizes the figure of the curator. For instance, in an essay referencing the concept of the curatorial, Anton Vidokle understands the figure of the curator to be dominant over that of the artist in terms of the originator of art; hence, he finds the concept of the curatorial useful only to re-inscribe the power position of the curator (~authorship ~collaboration). The name itself is quite unfortunate, as it does seem to focus on the curator. Yet, the concept endeavors rather to denote a particular way of working, involving many participants and different levels of collaboration. In this way, the curatorial has the potential to become an encompassing idea within the contemporary art and cultural field.
References and Further Readings
 Maria Lind. “Performing the Curatorial: An Introduction.” Maria Lind ed. Performing the Curatorial—Within and Beyond Art. Berlin: Sternberg Press, 2012; Chantal Mouffe. On the Political. London, New York: Routledge, 2005.
 Irit Rogoff. From Criticism to Critique to Criticality. eipcp. European Institute for Progressive Cultural Policies, 2003.Web, 2. Nov. 2012.
I rit Rogoff, ‘Smuggling – An Embodied Crticality’. eipcp.net. European Institute for Progressive Cultural Policies, 2006. Web. 2. Nov. 2012. http://eipcp.net/dlfiles/rogoff-smuggling. Also Irit Rogoff, Beatrice von Bismarck, ‘Curating / Curatorial’, Beatrice von Bismarck, Jörn Schafaff, Thomas Weski (eds.), Cultures of the Curatorial. Sternberg Press. 2012. pp. 21 - 38.
 Maria Lind, The Curatorial. Artforum October 2009. p. 103. Also Maria Lind (ed.), Performing the Curatorial – Within and Beyond Art. Sternberg Press. 2012.
 Paul O’Neill, ‘The Curatorial Constellation and the Paracuratorial Paradox’. The Exhibitionist No. 6. 2012. pp. 55 - 60.
 Irit Rogoff – Beatrice von Bismarck 2012 Curating/Curatorial. In Beatrice von Bismarck, Jörn Schafaff, Thomas Weski eds. Cultures of the Curatorial. Berlin, Sternberg Press, 21-38
 Ibid., 24.
 Vanessa Joan Müller, ‘Relays’. The Exhibitionist No. 4. 2011. pp. 66 - 70.