Paclets are Mathematica's native package format. They're effectively ZIP files with metadata that may be managed via the functions in the  ```"PacletManager`"```  context.

You can read much more about paclets  [here](https://mathematica.stackexchange.com/q/131101/38205)  or  [here](https://mathematica.stackexchange.com/questions/132064/pacletinfo-m-documentation-project?noredirect=1&lq=1) . This is a paclet server which you can read about  [here](https://www.wolframcloud.com/objects/b3m2a1/home/building-a-mathematica-package-ecosystem-part-1.html#main-content) .