This is one of the most common phrases amongst Cubans in Miami. It's the same as saying, 'what's up' or 'what's good.' This phrase can also be said as: que bola, asere. Asere is just another word for friend/bro/dude.
Examples of How to Use the Word:
Ayy mami, que bola!? Welcome to the party!
Que bola, asere? I haven't seen you in a long time!
I can't even tell you how perfect this music video is...