Why did I throw up yellow liquid?

This morning I woke up not feeling quite right. I started feeling very nauseous, and driving in the car for a while made it worse. When we got home I got the urgent feeling I was going to throw up so I ran to the bathroom and threw up yellow and clear liquid. Pretty sure it was bile. I hadn't eaten anything at all. It was about 10 in the morning. After wards, I felt better and ate a few chicken fingers and have felt fine since. But moving around a lot brings the feeling back a little bit. Why did I throw up?