Struts vs shocks

What's the difference between struts and shock absorbers?

the strut is the whole assembley, the shock is just the gas filled part

edit: I shouldnt reply when ive been drinking

LOL Nice but okay, that makes sense then. Here's another question....how complicated is it to change the shocks? The clunking noise in my car is horrible and I really need to get it fixed....and I will just change the strut mount at the same time as it could possibly be the cause as well. Has anyone attempted it before?