typically yeah.... its a quieter snare
mainly when people say ghost snare they will be talking about a quieter version of the original snare but theres more to it than that
on a real drumkit, ghost snares hits are not turned down versions of the original snare sound..... they are hit softer and have a totally different sound...... bear this in mind when programming beats
but of course, when making d&b, the goal isnt always to make natural sounding beats and theres loads of ways to make different sorts of ghost hits.....
a ghost hit doesnt have to be quieter.... maybe you could tweak the envelope and make it shorter.... perhaps change the pitch a little.... use different drums or whatever
if your after natural sounding ghostsnares & shuffles, you will probably get best results cutting up breaks...... or perhaps buy an acoustic drum kit
in answer to your other q's.....
percussion is a term used for a wide range of instruments, played rhythmically rather than harmonically........ think bongos, shakers, wood blocks and triangles
there are also percussive instruments that are played harmonically... like the xylophone for example..... but generally, when people say percussion they mean bongos and the like
and a cymbal is one of these.....
im sure you know the noise they make right???
theres different types.... its not that important for you to learn them yet but it will help in the long run....
the most common are crash's (which sound like their name), splash's and rides....... hi hats are also cymbals but generally they are in a different catagory to other cymbals
.....ive just thought....... the names are pretty pointless with hearing the sounds so i might as well stop going on about it....... but have a look through your sample collection and see if you have different cymbals and you'll see what i mean