Bridges as a product no longer exist due to how the market evolved. Typically the products specifically called bridges were used in hubbed environments to separate the collision domain or to bridge two network media types together (for example, Ethernet and token ring).
Bridges as a function are definitely still around.
Simply speaking, as a function of separating the collision domain, a switch is a bridge with lots of ports.
For an example of bridging two network media types, access points are bridges that bridge 802.11 traffic to Ethernet.
This will be a bit of a layman's answer, rather than quoting spec, but it should be accurate.
The collision domain is the sum total of the network segment (hosts, hubs) affected by the collision, and forced to deal with it by a random backoff delay.
Anytime a collision is detected on an Ethernet line, any and all interfaces on that line are required to stop transmitting. They each then come up with a random amount of time to wait before transmitting again, in an attempt to avoid another collision. In a crowded network, this delay will start to add up very quickly, and the collision domain is essentially the sum total of equipment that delay affects.
As in your quote, it comes up a lot less these days. The original Ethernet gear that filled the role of the switch was a hub, which simply repeated any frame sent to it out all of the other ports. Once a network got even lightly congested, this made collisions a common symptom. Modern switch technology virtually eliminates that problem, since any frame received by the switch is only sent to the host it's intended for. The only possible collision is between a host and the switch, making it a very small collision domain, affecting only that host.
Best Answer
A bridge (a switch is a high-density bridge) can help reduce the number of devices in a collision domain by breaking a single collision domain into multiple, separate collision domains with fewer devices on each collision domain than were on the original collision domain.
Each interface on a bridge is a separate collision domain. Assuming you were replacing a hub, where every interface is in the same collision domain, with a switch. Suddenly, you have more collision domains, but there are less devices on each collision domain than were on the original collision domain.