Apparition is a magical method of transportation and is basically the magical action of traveling by having the user focus on a desired location in their mind, then disappear from their current location and instantly reappear at the desired location. It is by far the fastest way to get to one's desired destination, but is tricky to pull off correctly and disastrous if botched up.
A Licence to Apparate is required to practise Apparition legally. One must be at least seventeen (17) years old to obtain such a licence. Lessons in Apparition are available, for an additional charge, to students who are or will be of legal age when the next test is administered.
[Harry Potter Wiki]