[tacomonstrous]

Riemann surfaces are algebraic, but their moduli can mean two different things:

a) the (algebraic) moduli space of complex Riemann surfaces of a fixed genus (number of donut holes). This is an object in the realm of algebraic geometry in that it is possible to embed it into complex projective space, using for instance theta functions.

b) the moduli of complex structures on a fixed topological surface of genus g: this is Teichmuller space, which as far as we can tell only an object in differential geometry. However, Eskin, Mirzakhani, Filip and others have discovered that various subspaces of this non-algebraic space are 'naturally' algebraic (or more precisely quasi- projective). This is the surprising part.