If i have an unlocked iphone will it work if i put my vodafone sim into it?

Okay so I'm getting an iPhone 4S for Christmas and my mam is buying off the apple website, it says it's unlocked so If I put my vodafone sim into it will it work straight away or will I have to bring it in to the vodafone store and get them to do something to it?

You put your sim in and it will work straight away.

Factory unlock means permanent carrier unlock. It means you can use any carrier sim of any country without any difficulty.

Yes it will work.