This site is called Socrative. The url is beta.socrative.com.
It allows you to create quizzes and tests for your students to take on the Internet and then it grades them for you. Here is my class taking a math quiz all on different devices. (It’s a website, so you just need Internet!)
You also have live feedback, which is super cool! As the students answer each question, I see them pop up on my computer as right or wrong.
I can then do a review immediately after they take the test. Talk about timely feedback!