Of the three aspects the Mother is the one with the clearest place in the ritual calendar, because the full moon is the fixed point around which Wiccan working is organised. The Esbats, the full moon meetings, are distinct from the eight seasonal sabbats, and they are the ordinary business of a coven in a way the sabbats are not. The Goddess addressed at an Esbat is the Goddess at her fullest, and that is the Mother.
The attributes attached to her are fruitfulness, protection and abundance, and in practice she is also the aspect associated with responsibility: the phase at which something has been brought into being and now has to be maintained. Widely read Wiccan authors are careful to say that motherhood in this scheme is not restricted to women who have borne children, and treat it as a posture of care and creative fullness available to any practitioner.
The best known rite involving her is Drawing Down the Moon, in which the High Priestess is understood to become a vessel for the Goddess during the working. Practice around it varies a great deal between traditions, from an invocation performed by a trained priestess alone to a working the whole circle supports, and the reported intensity ranges from a mild sense of inspiration to something closer to possession. The specific wording used is each coven's own and much of it is either oath bound or in copyright, so the atlas records the structure of the rite and not its text.