Using External Microphone on MacBook?

So I have read a few posts that say you need a device or software that will power the mic, not just plug it in the MacBook itself, which I feel is absurd. Either way, I was wondering what kind of device that is, specifically. I purchased 5 mics and 5 input/output splitters for podcasting at our school. Will this work? Or will I need something else/a new mic?

Thanks for your help.

-Luke