Defiant

My friends and I play a modded Server, but I can find No documentation on what these effectually mean for the game. A week or so Ago I had watched a Video that did an awful job explaining it to where only Mods that where Labeled as "Both" where Modded-Multiplayer Compatiable. The Wiki is a desert when it comes to any sort of information on the differences of these, help would be greatly appreciated