Sell is a verb and sale is a noun:

I'm going to sell my car and buy a new one.

She's selling bottles of water at the football game.

Yesterday I sold all of my old college textbooks on the internet.

The bookstore is having a Christmas sale - everything is 20% off.

(20% off = 20% discount)

The sales of our new product are slowly increasing.

This watch is normally $100, but it's on sale for $70.

(on sale = there is a discount)

There's also a pronunciation difference between sale and sell.

Greatest Concept Cars Ever

Ford GT90

Leaving aside that dated background, its hard to tell the spaceage Ford GT90 was first revealed to the world more than 17 years ago. Pumping out 720bhp from a quadturbocharged V12, it could accelerate to 60mph in 3.1 seconds and up to 100mph in 6.2 seconds, before going onto a lightning top speed of 235mph. Were talking Bugatti Veyron performance, but way before it even existed.

Because of the heat spewed out from the V12, the spiritual successor to the GT40 was said to use Space Shuttle ceramic tiles to keep the exhaust from melting body panels.