In my voicebank distribution, you would find the (pitches) next to their names. For beginners this is the page to make you understand what they mean.

Monopitch:

Monopitch voicebanks are voicebanks recorded in only one pitch, if a voicebank is monopitch it will sound more robotic and less natural. However they are less long to make since you only need to record the method once.

Bipitch:

Bipitch voicebanks are voicebanks recorded in two pitches, two pitches can make the voicebank a bit more natural and making one takes twice the time of making a monopitch voicebank.

Tripitch:

Tripitch voicebanks are voicebanks recorded in three pitches, three pitches can be enough to form a powerscale voicebank (in my opinion that is) since the lowest pitch can be the softest along with the middle pitch being a core pitch and the hightest pitch being the most powerful. Three pitches are enough to make a natural sounding voicebanks (again in my opinion).

Quadpitch:

Quadpitch voicebanks are voicebanks recorded in four pitches making the voicebank very natural sounding, a good example is Namine Ritsu's Kire bank recorded in A3, D4, G4 and C5. A3 being soft, D4 being natural, G4 being strong and C5 being very powerful! This is the most recommended option as this makes the voicebank more than slay.

Multipitch:

Multipitch voicebanks are voicebanks recorded in five or more pitches, this is a name also given to bipitch, tripitch and quadpitch voicebanks despite being less related. These voicebanks are the most natural sounding ones but takes very long to make one due to the amount of pitches, these are also mostly made for Japanese voicebanks since they're more simple to make.

Multiexpression:

These voicebanks are multipitch or monopitch voicebank with appends recorded in the same pitches, if the append is monopitch it is less considered multiexpression (in my opinion). A good example is Namine Ritsu's 何かがキレ voicebank (recorded in A3, D♭4, F4, A4, D♭5, A3弱, D♭4弱, F4弱, A4弱, D♭5弱, A4強, D♭5強, and もやし).