The Batalin--Vilkovisky formalism, developed in the '80s, is a useful tool in the perturbative quantization of gauge theories. A key feature of this procedure is the enlargement of the already infinite-dimensional space of fields by extra fields with opposite parity. In this talk, I will give a short review of BV and its geometry, with emphasis on the algebraic aspects (homotopy algebras, cohomology), and then discuss some examples like Chern--Simons theory and a field theory for the Beltrami differential, for the deformations of complex structures.