It does exactly what it says. It encrypts the text you enter into various formats, including binary, hex, leet speak and so on. It's usefullness is completely up to you. If you need something converted to ascii or binary and are unable to do it yourself, then it's very useful. You can use it to find the related values. If you have something that's encrypted on your machine and don't have the decryption tool, if the scheme is available from the text encrypt, you can decrypt your text there.

Btw for future reference it isn't 'wut', it's what.