Q:

What is a bobber?

What is a bobber and are there advantages for turning your motorcycle into one as opposed to running it stock?

A:

Bobbers have particular characteristics and styling that define them as a bobber.

Very stripped down for weight reduction to increase in power to weight ratio
Removal of the front and rear fender
Removal of passenger related equipment (seat, passenger footpegs)
Frequently a hard tail with the rear suspension removed and replaced with hard struts
A shortened seat height
A cut frame to reduce seat height and remove unnecessary items

A bobber will typically not have:

A raked front end like a chopper
Liquid cooling for the engine (this isn't a must but a frequent)

A:

A bobber is simply a stripped down motorcycle. The name comes from the term "bob-job". Which was something done in the early days of racing to reduce weight. Bobbers are normally american motorcycles, but it can be done to any brand.
The advantages are less weight. But these days a motorcycle's aero is too important to ignore since it impact performance and safety at speed. I would not do it too much to a modern bike because they are too uncomfortable!

