Diagrams or yantras are used to visualize deities during worship.
Images are also used in worship as receptacles for the divine. The use of imagery in Hinduism contrasts with the Abrahamic or Western religions (Christianity, Judaism, Islam), where direct worship of images is disallowed.
For this reason, these three classes were known as dvija or “twice born.” The lowest castes (shudras and untouchables) were excluded from this.