[Scallywag]

OK, I have another rifle-related novice question, and this site has become my #1 place to ask these kind of stupid questions and get educated. So here goes:

Can anyone explain to me the importance of the rate of twist in a firearm barrel, and why it's different for different calibres? I get the importance of rifling, but the twist rate is baffling to me. I guess the barrel length is related to this, too?

What would happen if you had the 'wrong' rate of twist in a barrel for the ammunition you were using?

Can someone explain the principle behind it, as dumbed down as you possibly can?

Thanks as always.