If you're looking for the main Carbon project, see https://github.com/carbon-language/carbon-lang/.
This is an archived copy of the explorer codebase. It was forked at commit
76c68153,
which is tagged as
explorer-archived
in the main carbon-lang repository.
The explorer was a prototype implementation of the Carbon language, and uses an AST-based approach in its implementation. The explorer is not complete; it was a partial implementation when development stopped, and the design has since evolved.
See proposal #5270: Move explorer out of toolchain git repository for additional context.