The foundations of the general theory of relativity are presented, an introduction to its modern development and state is given. The necessary mathematical apparatus is set out quite fully, but without overloading with details. The basic principles and consequences of the theory, its experimental and observational status are discussed. An idea of ​ ​ the current state of the general theory of relativity and its applications to astrophysics, black hole physics, cosmology is given. Possible extensions of the theory and ways to test them experimentally are discussed.