Originally Posted by Jaywalk3r

Can't they just be bikes?

Look, pick a bike, any bike; it doesn't matter (so long as it's of decent quality). Whatever you pick, there's going to be some things it's really good at, some things it's pretty good at, some things it will do okay in a pinch, and some things it's not so good at. You might have to swap out tires or a component or two, but most bikes are pretty versatile. There's a lot of overlap in capabilities. The key is to find a bike that does really well whatever you're going to task it with most and does pretty well or at least adequately the things you'll ask of it only occasionally. Everybody falling for the idea that we need a specialized bike for every single cycling task we might have is a marketing department's wet dream.

Originally Posted by Sixty Fiver

Some mountain bikes have 700c wheels and some urban bikes have 26 inch wheels.