The primary role of the altar server is to assist the priest in the celebration of the liturgy during Mass. This is done through specific actions and by setting an example to the congregation by active participation in the liturgy, i.e. joining in the singing of hymns and responses, and by looking alert and sitting or standing at the appropriate times.
Servers carry the cross, hold the book for the priest when he is not at the altar, carry the incense and censer if used, and present the bread, wine and water to the priest during the preparation of the gifts. The server also assists the priest after he receives the gifts from the people in the washing of hands prior to the beginning of the prayer of consecration.