The Arithmetic Guru game has lots of names. It's the numbers round from Letters and Numbers, it's similar to 4 4's, sometimes it's just called an arithmetic puzzle.
You are given a few numbers and a target number. Your goal is to use any arithmetic operators on your starting numbers to create an arithmetic expression that equals the target number.
Some variants of the game let you use square-roots, exponentiation, factorial, floor and many other mathematical operations.
The Arithmetic Guru is how you cheat. It tries every possible arithmetic operation in the basic version (plus, minus, times, divided by) and therefore comes up with every possible answer.