Is there a guide for Ionic Markup tags? Or can someone explain them?

This seems like a simple thing… but I am a bit confused by the <ion-…> tags. Like when to use them, if you have to, what they do, and where a list of them are. I was going through this guide ( but it shows the useage of divs. Any help in pointing me in the right direction is appreciated - thanks.

Okay it seems to be directives.