What is a 408???

So I keep hearing about the 408 stroker. I know it starts as a 360 but what do you do to make it a 408? Is it expensive? Just wondering cuz I bought a 360
408 is kind of a vague description of a small block la engine with a 4" crankshaft. The displacement will very with bore sizes but yes, a 408 has its stroke increased to move it from a 340/360 to over 400 ci.