Magsafe is a type of power connector developed by Apple. You can find out more about Magsafe products either on-line at a site such as Wikipedia or by visiting an Apple store.

Apple actually makes this part themselves, as they do not license the MagSafe technology out to third parties. You can get the MagSafe adaptor at any Apple store for $49. The part number is MB441Z/A.

It is the new charging port for Apple MacBooks.

Because Apple is a power hungry and greedy company that pattented their "magsafe" technology with such a high price tag that no one else would consider paying for it.

No, you cannot use an Air charger with a Macbook Pro. It has a different power rating (watts). New Macbook Pros and Airs also feature a different, smaller connector for power (Magsafe 2).