When can I make my own group?

What is it called when you have a certain group of letters, then see how many words you can make out of them?

• Example: you have a group of letters like: "atr" then you find all the words that can be made, like: "art, rat, tar". Does this have a name?

• Answer:

  If you only have to rearrange all of the letters, as in the example you have given, such puzzles can be called anagrams, unjumbles or unscrambles. I've also heard them called text twists.