What is the difference between an ollie and a fakie ollie?

An ollie is when you pop off the tail of your board in your normal riding stance while going forwards.

A fakie ollie is when you pop off the nose of your board in your switch stance while going forwards.

All in all its the same trick except that with a fakie ollie you are doing an ollie but instead of going forwards you are going backwards.

I hope this helps