There are some predefined preprocessor macros (specified in C and C++ standard) like __line__ and __file__ which are replaced by line number and file name during preprocessing respectively. In C++20, a new class std::source_location is introduced which does more or less the same thing.
Preprocessor macros live outside the type system. Preprocessor macro substitution happens outside the rest of the language. See this answer and this answer for a comprehensive discussion of the disadvantages of using the preprocessor.
std::source_location on the other hand behaves like any other C++ struct. It has plain value fields that are typed and behave like any other values in the language.
Besides that, functionality-wise the two mechanisms are equivalent. There is nothing that the one can achieve that cannot be done by the other (apart from the column field in source_location, which has no equivalent in the preprocessor). It's just that the new approach achieves its goals more nicely.