What is general relativity?
General relativity is a physical theory about space and time and it has a beautiful mathematical description. According to general relativity, the spacetime is a 4-dimensional object that has to obey an equation, called the Einstein equation, which how the matter curves the spacetime.
What force is explained by general relativity?
General relativity explains gravity, and in this theory, it is not really a “force” anymore. The gravitational field comes out of the description of general relativity as a result of the curved spacetime.