Adventure mode in Minecraft?

There's survival, creative and hardcore, but I've never heard of adventure mode before. I tried it out and to me it was the same thing as survival… Unless I didn't try much. What is the difference with adventure mode and other modes?

Adventure mode only let's you break glass, It was made for custom maps.

The main difference to survival mode is that you can't break most blocks without the correct tool.

Example:

A shovel is required to break sand or dirt
An axe is required to break wooden blocks… And so on.