K-pop identity crisis - how to tell the difference between k-pop stuff with the same name

It's always confusing when k-pop stuff has the same name.  How to tell the difference between idols, groups and other k-pop things these days?

Never one to shy away from tackling the big issues, Kpopalypse is here to help!  This post will list some stuff with the same name or similar features, and use helpful questions and answers to highlight the important differences between them!  Yay!