Okizeme is just a blanket term for your options post-knockdown and, by association, a term for your offensive options when they are knocked down.
In Tekken 5 DR, for instance, if I'm Ganryu and you've just gotten d+1'd, you can choose to:
A.) Tech, in which case I can probably go for a crossover jumpkick tech-trap
B.) Lay there, in which case I can hit you with whatever I want from d,f+3 to 1+2
C.) Roll to the right/left, in which case I can nail you with d+1 and any move that tracks in the correct direction.
D.) Get-up kicks, in which case I can block and re-launch that ass.
E.) Back roll, in which case you can eat a f+2, a dash 1+2 or a dash d+1+2, etc
etc etc etc
There are counters for everything, and counters for those counters. Knowing your options and how your opponent plays wake-up situations is tantamount to domination.