This website is a guide for how to choose/distinguish between common types of bicycles and their purposes.

http://gobiking.ca/resourceshow-to/choose-the-right-bicycle-for-you/

Provided by Gobiking.ca (cycling in Ottawa-Gatineau), much information is provided about various bicycle styles: 

Mountain, Hybrid (comfort), 
Hybrid (performance/training), 
Road (relaxed geometry), 
Road (touring), 
Cyclocross, and 
Road (high performance/racing), 
Additional information about frame types and gears, speeds, and components.