Generally, a bridge has only two ports and divides a collision domain into two parts. All decisions made by a bridge are based on MAC or Layer 2 addresses and do not affect the logical or Layer 3 addresses. A bridge will divide a collision domain but has no effect on a logical or broadcast domain. If a network does not have a device that works with Layer 3 addresses, such as a router, the entire network will share the same logical broadcast address space. A bridge will create more collision domains but will not add broadcast domains.
A switch is essentially a fast, multi-port bridge that can contain dozens of ports inside a Cloud Hosting or a Website Hosting that has a Dedicated Server on it. Each port creates its own collision domain. In a network of 20 nodes, 20 collision domains exist if each node is plugged into its own switch port.