The Teichmüller space of a (closed) 2-dimensional manifold is the moduli space of complex structures on , where two complex structures are identified if they are taken into each other by a homeomorphism which is isotopic to the identity.
Since the diffeomorphism class of a closed manifold of dimension 2 is given by its genus , typically one speaks of the Teichmüller space for each . More generally one considers s equipped with punctures/boundary circle and then writes .
Teichmüller space is a covering space for the moduli space of curves over the complex numbers (see below). When also the singular nodal curve is included one speaks of the augmented Teichmüller space which in turn is a cover of the Deligne-Mumford compactification of the moduli space of complex curves.
Teichmüller space itself carries a complex structure.
Review includes (Schumacher, section 2)
Quotienting the space of complex structures on by all homeomorphisms produces what is called the moduli space of curves (over the complex numbers). Closely related to the moduli space of conformal structures hence of Riemann surfaces.
The original articles are
Oswald Teichmüller, Extremale quasikonforme Abbildungen und quadratische Differentiale, Preußische Akademie der Wissenschaften, nat. Kl. 22 1-197 (1939)
Oswald Teichmüller, Veränderliche Riemannsche Flächen, Deutsche Math. 7 344-359 (1944)
The complex structure on Teichmüller spaces was fully established in
L. Ahlfors, The complex analytic structure of the space of closed Riemann surfaces, in Analytic Functions, Princeton University Press (1960)
Lipman Bers, Spaces of Riemann surfaces, Proc. Int. Cong. of Mathematics 1958, Cambridge 1960
Georg Schumacher, The theory of Teichmüller spaces – A view towards moduli spaces of Kähler manifolds (pdf)
Wikipedia, Teichmüller space
Further developments include
Alexander Grothendieck, Techniques de construction en géométrie analytique. I. Description axiomatique de l’espace de Teichmüller et de ses variantes Séminaire Henri Cartan 13 no. 1, Exposés No. 7 and 8 (Paris: Secrétariat Mathématique). (1960/1961) (Numdam)