This is an enchantment that allows you to communicate between clientside and serverside a bit easier. If you know how to work with events, then you probably do not need this, but it has some nice features which allows you to sit back and write less code + achieve some nice results.
Note: It is important to keep in mind that this is an enchantment. Which means it is just an layer on top of the basic functionalities of MTA. And most enchantments come with a