It's a computer who grants or denies you credit based on a matrix. When you apply online, it goes and checks your credit score with a credit bureau and then based on the matrix approves or denies you.
Sometimes, when the system is down or you're on the bubble, then it'll give you a notice saying they can't approve it online, but will take 7-10 business days. In cases like this, the application then goes to a live person who will evaluate your score and other factors.