Board Thread:Questions and Answers/@comment-99.244.188.226-20130605034528/@comment-3076833-20130823002759

"Extend" could be described as an "Add-on" to the vocals. Think of it like a stack of bricks where 1 voicebank is a brick. You can have as many of these "bricks" as you like for your main vocalist (Like Gumi) to make a tower of voices for them.

"Append" would be much closer to your "Expansion pack" where you're adding more voices to a starting voice for a vocalist (Like Miku). Think of it like a game where you have the main game and expansion packs to add onto the gameplay.

"V3" is simply the term used to refer to old vocals that have been upgraded to the Vocaloid 3 engine. In some cases (Like Kaito and Gakupo) more than 1 voicebank was in the software release but not all (Like Lily).

Sorry if the examples above sounded weird but it's the best way I could describe them. :S