Conceals things from view and obfuscates inherent magical properties of objects
Concealment Charms (incantation unknown) are spells used to conceal things from view and to obfuscate inherent magical properties of objects.
Sometime in the early 20th century, Minister for Magic Ottaline Gambol allowed a secret operation to obtain a train to be used as a means of transport of Hogwarts School students to the Castle and back, on the beginning and end of term, respectively. This operation ended up involving one hundred and sixty-seven Memory Charms and the largest ever mass Concealment Charm performed in Britain, while several bemused Muggle railway workers in Crewe spent the rest of the year grappling with the uncomfortable feeling that they had mislaid something important.
In 1996, when Harry Potter speculated that Draco Malfoy had sneaked a cursed opal necklace by Filch's Secrecy Sensor, Hermione Granger said that Secrecy Sensors picked up concealment charms easily.