Plugin question

HI, i am a total noob beginner with unity and i have fixed planes what i would like to do with unity but i have no clue if all of it is possible to do. Is there a way when i made a game with unity does the community could write plugins / mods what add features into the game? Best example would be like minecraft with the mods! Don't get me wrong here, i don't want to know all the how and how to do... just if something like this will be possible, and i will find out the rest. But i couldn't find an answer for this yet.