Whats the difference between a half cab ollie 180 and an ollie 180 i think they both look the same?

The term cab comes from an old vert skateboarder called steve cabbellero who invented a trick called the cabellariel which was basically a backwards 360. A half cab is half a cabellariel a backwards 180, ollie 180 is frontside. So if you ride regular to half cab you would spin the left, and for a regular 180 to the right etc. Hope this helps good luck with the riding.