OK....I've sussed out that a nacelle is a 'housing' which typically will hold an engine. I've also checked an MD90 and noticed the larger engines, which are labelled as Boeings.
The MD11 is distinctive, but it looks very similar to a DC-10. Only differences I've noticed are winglets on the MD11 and the wing engines do look different but I'm not sure.
On another note, I was watching some video clips of a/c landing and I noticed a 737's nacelles splitting just after touch down. I've never seen that before. Is that common to all engines, or just some? Is it to do with reverse thrust or brakes or something else?