This is a mega-repo for housing the http-client family of packages for Haskell. These packages provide a low level HTTP client engine (http-client), different backends for providing SSL support (http-client-tls and http-client-openssl), and higher-level APIs for user convenience (http-conduit).
If you're just getting started, it is recommended to use http-conduit, which is documented in the Yesod book.