lol unless you actully start to mix or master these terms can only be experienced. Audio like anything else has texture. Vocals can be too thin and need some fatting up. When this term is used the vocals need a little bass or something to give them more of a presence in the mix. Sometimes its not the eq, you could have some phasing drowning out a sound. what ever the case these terms are picked up over the years of working with sound and what it does. but i did find this glossary of recording terms if this helps a little more.
http://www.tape.com/Bartlett_Articles/recording_terms.html

thanks. thats a start.