Bhop
A normal bhop works by the same processes as in any other game. However, in Overwatch it is guaranteed to lose you speed.
Execution
B-hops are very easy and intuitive. All you have to do is press jump on the frame you're landing on the ground. You can hold the jump input as long as you want after that. Compared to other games wiggling your aim, or similar, does not give you a speed boost, but actually loses you speed at a certain point.
The mechanic behind b-hops is the same as the one behind skims and lateskims. Touching the ground will slow you down, however Overwatch does not kill your entire momentum in one frame, but over a longer period of time, so cutting down the time for which you touch the ground allows you to keep most of your speed. You can chain around 10 perfect b-hops after each other until you've gone from max speed to walking speed. Due to the nature of the tech b-hops are only useful if your speed is higher than walking speed.
Pros and Cons
B-hops are a good way to keep your momentum alive when there are no walls around. They require no setup, can be chained, and are easy to perform. However glaring lack of speed build up makes them subpar for any situation where you could instead do any kind of jump or any of the later advanced techs that build up speed.
Tips
B-hops, like many other techs, can be made significantly easier with jump bound to scroll wheel. In this case, you just need to scroll when near the ground and you'll most likely get the frame perfect jump input for the b-hop.