Four.

In most states, if the scooter is 50cc and under - you need a driver's license.
Any higher and you will need a motorcycle endorsement on your license.
It's not the point that it's a scooter or a Vespa. It's the size of the motor that determines that.

also, please explain the restrictions etc. please give me answeres specifically to 50cc mopeds, motorized scooters, Vespas etc.

Thanks.

I'm thinking of buying one of those scooters to get around the city and to work every once in a while. I noticed that they sell them in the mall near my house and there are even small dealerships.
But do I need to get a motorcycle license to drive one around legally? what about insurance?

Just curious. I couldn't find it anywhere on the DMV website.