A Collision Domain is any network segment in which collisions can take place (usually in Ethernet networks). If there is more traffic in on a collision domain, the chances of collisions are also more. Increased collisions will result in low quality network where hosts spending more and more time for packet retransmission. Usually switches are used to segment a collision domain.
A Broadcast Domain is all devices that will receive any broadcast packet originating from any device within the group. In Collision domain, any type of data packet can encounter a collision, while in Broadcast Domain, we refer broadcast packets. Usually Routers are used to segment broadcast domain.