Lie Algebras is a useful tool which dominates every aspect of the interaction between physics and mathematics. Moreover, the applications within mathematics are uncountable and some of them will be discussed throughout this talk. Gravity will be given especially to the algebraic setup of these algebras and some results from algebraic topology such as Lie’s III Theorem which establishes a very good relation between Lie Algebras and the geometry of Lie groups. Categorical aspects such as the category of modules over the universal algebra U(g) of a lie algebra g will be discussed too.