What is the "Need for Speed Carbon" CD key?

According to Electronic Arts, the "Need for Speed" CD key is the registration code that comes with the copy of the game. It is required to play the game and to unlock online features.

The registration key can generally be found at the back of the CD case or at the registration instructions. "Need for Speed" is an interactive racing video game published by Electronic Arts. The very first game of the series is named "The Need for Speed" and was first released in 1995. The developer had subsequently released several episodes yearly. The game is available for play on several platforms, such PCs, gaming consoles and handheld devices.