When you are out buying your computer, you will have the option of either a dedicated video card, or an integrated video card. 

If you are into playing computer games, chances are you would opt for a dedicated card.  If you just work, type, surf the Internet and check some emails on your notebook, an integrated card will do fine.

What does a video card have to do with battery life?

Simple.  If you want better battery life, an integrated card will give you the most battery life, whereas a dedicated video card will give you the least battery life.