Tube bending is a self-explanatorily-titled process, with results that show up in everything from your car's exhaust system to your bicycle's handlebars to the conduits in your home. It can be done by hand, a bending machine, or Superman when he's showing off. To see the process in action, let's take a quick look at this Society of Manufacturing Engineers video:
To help control the amount of the bend and prevent wrinkles, a mandrel can be inserted inside the tube prior to bending. As you can see below, there are several different types of mandrels:

Tube bending can be used to make trombones, grab rails, SUV bumpers, and bad guys angry.

"My grandfather gave me that rifle...thanks a lot."
Comments
@ 44 seconds in. Guy's shirt reads:
"If you don't want to get muddy,
Stay home with the wife."
HA!