HTML5 is not one big set of feature, but instead it is a set of individual feature. Each browser supporting a subset of it. Which just makes it more difficult to build using it... HTML5 adds new tags *and* corresponding API in the DOM (Document Object Model).
- Video - to play video without extra plugins.
- Local Storage - to hold a lot of data on the client.
- Offline web application - to download web elements and store locally.
- Geolocation - to know where the client is.
- Input types
- Placeholder text in input fields