Halfcab - A fakie backside 180 ollie or half a caballerial. A halfcab is a modifier trick. That means that any trick done with a fakie backside 180 in it could be called a halfcab.
Learn kickturns from fakie to regular, ollies and 180 backside ollies (maybe try this trick before you learn backside 180 ollies).
This trick is done from fakie to your normal stance. This makes popping it pretty easy. You can rotate around the back truck before the pop and after the land. That works for a tiny ones when you are learning.
For a bigger one you will need to wind up your body and pop as high as you like. A lot of the rotation happens when you are past the peak of the ollie. This gives time for a nice tweak and good style.
Try to land with all 4 wheels at once for style points.
Practice landing on the back wheels or the front wheels to get you ready to land in grinds, slides or manuals.