The Thursday of Holy Week recalls the Last Supper of Jesus with his friends before he was arrested, during which he inaugurated the Eucharist/Holy Communion.
Traditionally a special service is lead celebrating Holy Communion and afterwards stripping the altar and church of all decoration. There is a tradition in some places of foot washing, as descibed in St John's Gospel, and a vigil of prayer is often kept, in re-enactment of the Garden of Gethsemane.
There is no formal end to this service, and the people just 'drift away'.
Traditionally the Priest wears gold or white vestments at this service.