I don’t know. I just wondered if the two expressions may be used interchangeably. For example would it be correct to write the following:
1. “I usually go to work by bike”
2. “I usually ride to work on a bike.”
If the sentences above are correct if there is any basically the difference between them?
I think the problem is that in order for the two sentences to mean the same thing, you need to add the preposition "on" where shown above.
In the first sentence, the word "by" tells you that the bike is the means, or method, of how you get to work. The second sentence doesn't work because on its own "a bike" just tells you what the object is that you use to go to work on, but the "on" is needed to convey the sense of how you use it as your means of travel. In the case of a bike you usually have to sit
on it to use it [unless you are riding in the Tour de France where you might stand up on the pedals, but even those riders sit down
on the saddle for most of the time].
In the same way other phrases could be used which follow the same pattern:
"I usually ride to work
on a horse" rather than "I usually ride to work a horse".
"I usually ride to work
on a motorbike" rather than "I usually ride to work a motorbike".