The altar server assists the priest in the celebration of the liturgy during Mass. Servers carry the cross, the processional candle(s), hold the book for the priest celebrant when he is not at the altar, carry the incense and censer, assist the deacon in bringing vessels to the altar, wash the hands of the priest, assist the priest celebrant and deacon as needed.
Below is a set of training tools to help prepare you for this role of service.