OK, I think it's getting a bit confused here.

AFAIK (in the guitar universe; not necessarily music-wide):

Tremolo = rapid picking of a note
Vibrato = the quick raising and lowering of the pitch of a note

However, things get more confused, even in the guitar world, when companies decide to make amps & effects that are called "tremolo" and they do a vibrato-type effect.

After doing a quick dictionary double-check, it seems that tremolo is produced by a pulsating effect, attained by rapid repetition of a note, whereas vibrato is (again) a tremulous or pulsating effect; however, it is attained by "minute and rapid variations in pitch".

Not trying to be a jerk or anything here, just trying to clear some things up in this discussion.