  In the first section we recall some basic notions on Lie algebras. In a
second time we study the algebraic variety of complex $n$-dimensional Lie
algebras. We present different notions of deformations : Gerstenhaber
deformations, pertubations, valued deformations and we use these tools to study
some properties of this variety. Finaly we introduce the concept of rigidity
and we present some results on the class of rigid Lie algebras.
