A repository containing TAPI plugins.
While this may sound complicated, don't worry because each computer with the .NET Framework about version 4.0 will have the C# compiler stored in [usually] the same location.
Within each plugin root folder is a little .cmd file that, when run alongside the .cs source file, will compile it into the desired .dll format.
Given, there's a requirement for each plugin to compile successfully, and that is the tShock plugin libraries. This is included in every tShock .zip file:
Include OTAPI.dll, TerrariaServer.exe, and TShockAPI.dll in the same folder as the plugin .cs and compile.cmd files.
A more thorough process of this can be found at the WIki.