ETOPS stands for Extended Twin engine OPerationS. Basically it means that twin engined aircraft can fly for long distances over water as long as they are within a certain amount of flying time from a suitable airfield should the aircraft suffer an engine failiure. Depending on the aircraft the times can be 60min, 80min, 138min, 180min or in the case of the latest B777 207mins.
As for aircraft certified for etops:-
A319CJ
A330
B737BBJ
B757
B767
B777
There are more to that list and I'm sure someone will correct me but that is the basics of it