How do you read Google Insight?

I read the “About” and “Working with Google Insights” sections but I still don’t understand. When I look up the term “Greek food”, the state of Arkansas indexes at 100. What does this mean? That my state searches for greek food more than any other state? That if you live in Arkansas, you have a 100 percent chance of searching for greek food?

When I drill into Arkansas and look at the “interest over time”, the index for greek food was a 0 for last month as well as the month before. Before that, it was a 17.

Can someone explain how they come up with these numbers?