Various options available to generate typos are...
1. Skip letters
2. Repeat letters
3. Swap letters
4. Miss letters
5. Extra letters/numbers
6. No spaces
7. Share generated typos with the url
All the options are further configurable by limiting number e.g., you can skip 1 or more letters or repeat 3 or less letters
One of the use of this is to identify common typos in popular domain names. Some people register such domain name and park it in order to generate revenue. It is very likely that user may make typing mistake in typing a domain name and visit parked domain instead.