Muggles' Guide to Harry Potter/Magic/Evanesco

Overview
Evanesco is the Vanishing Spell, used for causing an object to disappear, almost like Disapparition.

Extended Description
This charm is mentioned only in passing; it is used to make objects vanish and in the books is most often seen used for cleaning. In a number of places in Potions class, Professor Snape will use this charm to clear an incorrectly made potion out of a cauldron; on one occasion, Hermione used it to clear up a potion that Harry wasn't done with yet. It is also used by Harry to clean Hedwig's cage, in the seventh book.

In Harry Potter and the Deathly Hallows, Professor McGonagall is asked the question "Where do Vanished objects go?" by the Ravenclaw door-knocker, to which she replies "Into non-being, which is to say, everything." This suggests that Vanished objects cease to exist, until they are re-conjured.

Analysis
This spell seems to be used for cleaning things out of containers; Scourgify and Tergeo, while similar in effect, seem to be used for cleaning things off surfaces. Presumably there is a mental component of this spell, as well as the verbal and wand motion components: we expect that the spell caster must visualize either the resulting cleaned container, or (more likely) the objects he or she wishes to have vanish, when the spell is cast. Otherwise, it would be far too easy to clean the cauldron (e.g.) completely out of existence.