Finding similar words

Hey everyone.

I'd just like a super high overview on what the process is called, when you supply a string as an input, and the process returns you a list of strings that are similar to your input?

For example, many sites enable this functionality for usernames. Where you create an account and provide a username, if that username is taken, the algorithm parses all available names and return ones that are possible alternatives.

Is this something that natural language processing does? What is this algorithm or process called?

Cheers!