plugins are essentially shared snippets that extend functionality of quests.
https://github.com/ProjectEQ/project...master/plugins
I would recommend installing via Akka's installer, it will configure an environment to run eqemu with. Once that's done, it will pull down the latest plugins.
Documentation on the two languages used for quest scripting is found:
https://github.com/EQEmu/Server/wiki/Perl-API and
https://github.com/EQEmu/Server/wiki/Lua-API
Your questions more can be boiled down to learning lua or perl, once you understand them, all plugins do is give generic extensions that other quest files will refer to. Akka has released some additional plugins at times, mainly administrator tools, but it's not like plugins are magic black boxes. They're just existing code to help streamline some processes commonly used