---The above is taken from the General Instruction to the Roman Missal (Third Typical Edition)
Altar servers should receive proper formation before they begin their ministry. The formation should include instruction on the Mass and its parts and their meaning, the various objects used in the liturgy (their names and use), and the various functions of the altar server during the Mass and other liturgical celebrations. Altar servers should also receive appropriate guidance on maintaining proper decorum and attire when serving Mass and other functions.
Dress Code
Altar servers may wear an alb or other suitable vesture or other appropriate or dignified clothing. All male altar servers should wear the same liturgical vesture and all female altar servers should wear the same liturgical vesture.
Function at Liturgical celebrations.