Apparition is a means of transportation in the Harry Potter Universe. Its name is derived from the Latin "Appareo", meaning "appear" or "I become visible".
This spell allows the caster to appear instantly in a desired location. You must pass an Apparition Test before you are legally allowed to use the spell, which cannot be taken before the age of seventeen. Apparition lessons are available at Hogwarts during the 6th year. Learners are taught the three D's: Determination, Destination and Deliberation. When someone has Apparated, their appearance comes with a sound, ranging from a small pop to a loud crack. The sudden appearance combined with the sound often startles others.
Both the terms 'Apparate' and 'Disapparate' can be used in reference to Apparition; from the point of view of the caster, one always Apparates, however from the point of view of one observing someone Apparate away, it is referred to as Disapparating. These words are used in the same way as the words 'appear' and 'disappear'.
Splinching occurs when a use of the spell is unsuccessful - when the caster is not focussed enough, random parts of their body may be left behind. This can make Apparating very dangerous.