When referring to Car Engines what does "stroke it out" mean? and what is a stroker kit?

A stroked engine has had a crankshaft change to increase the "stroke" length of the pistons. A stroker kit includes usually a new crank and bearings at a minimum. There are limits in how much you can stroke an engine before you have the crank smacking the block but this can be fixed to a point by grinding away some of the block in the path of the crank. Of course with a great stroke length, the pistons come closer to the heads, requiring new pistons with deeper valve reliefs. Pistons could also be a part of the kit. Depends on the level of the kit itself.