Each of the three Gods in the trinity also has a female counterpart/wife/consort. Lakshmi is the wife of Vishnu. It is said that she is his strength and when Vishnu takes a body as an avatar, that Lakshmi becomes his consort on earth as well and that she is both Sita and Radha.
You can often recognize Lakshmi in pictures by the gold coins pouring from her hands. She is the goddess of wealth, both material wealth and spiritual wealth. The lotus that she sits or stands on is a famous symbol of being in the world but not tainted by it. A lotus floats over water but its petals do not become wet. It stays clean even in dirty water. This symbol being associated with Lakshmi is a reminder to enjoy the wealth of the world but not become consumed by it.
She is one of the deities who is worshiped during Diwali, the New Year.
Lakshmi is the embodiment of love, from which devotion to God or Bhakti flows. It is through Love/Bhakti or Lakshmi that the atma or soul is able to reach God or Vishnu. Lakshmi plays a special role as the mediator between her husband Lord Vishnu and His worldly devotees. While Vishnu is often conceived of as a stern, easily perturbed patriarch, Lakshmi represents a more soothing, warm and approachable mother figure who willingly intervenes in the lives of devotees on His behalf.