I got this off Wikipedia, seems pretty good:
Until the
Second Vatican Council, the
acolyte was the highest of the
minor orders, having as duties the lighting of the altar-candles, carrying the candles in procession, assisting the
subdeacon and
deacon, and the ministering of water and wine to the
priest at
Mass. Acolytes wore either the
alb or the
surplice. While acolytes did not receive the sacrament of
Holy Orders, they were considered part of the
clergy, and were a required step on the way to Holy Orders.
After the reforms of the
minor orders in 1972, the acolyte survived but became one of two
lay ministries (along with
lector) instead of an order, with its conferring rite renamed from
ordination to
institution to emphasize this. It was still confined to men alone but was
de jure now open to all men, even those not going into seminary. However, since
altar servers can do just about anything an acolyte can do, very few men outside of seminary are formally instituted. An instituted acolyte, though, does have some special faculties: he is a permanent extraordinary minister of
Holy Communion and can also be entrusted with celebrating Exposition of the Blessed Sacrament.
Indult Catholic societies such as the
Priestly Fraternity of St. Peter are permitted to ordain seminarians to minor orders, including the acolytate.
The term
acolyte may also informally refer to ordinary non-instituted
altar servers.