A chalice is essentially just a goblet or cup intended to hold drink, but, in religious terms, it is specifically a cup intended for use during a ceremony or ritual.

A chalice can me made of any material that YOU feel is sacred to yourself. Also what you hold inside the chalice should be equally scared. This can be anything from healing water, to liquor. Though Many spells do call for a specific liquid to be used. 

A chalice is often kept on your alter. There can be one or many depending on the ritual setting. You may want to have one for all to share, or one for each entity being acknowledged (and yes you count as an entity).