What is an Alkaline battery?

Question

What is the difference then a regular battery?

And what extra does it do?

Answer 1

Different chemistry.

The "regular" carbon-zinc battery uses an acidic electrolyte, while the alkaline one uses... alkaline.

Alkaline batteries have a greater capacity per volume than regular carbon-zinc, so they last longer. They also have lower internal resistance so they perform better in pulsed applications, like cameras and other high-drain loads.