Catchall is a feature that when enabled/configured will send any email address on the specified domain to be send to a specified forward address.
Example. if you have "wefixanything.com". Now you have 3 email accounts created (sales@wefixanything.com, quotes@wefixanything.com, shipping@wefixanything.com). If catchall is enabled if someone misspells an email sails@wefixanything.com, or anything like stupids28392@wefixanything.com you can configure all those email addresses to be forwarded to a specific email address.
Example. if you have "wefixanything.com". Now you have 3 email accounts created (sales@wefixanything.com, quotes@wefixanything.com, shipping@wefixanything.com). If catchall is enabled if someone misspells an email sails@wefixanything.com, or anything like stupids28392@wefixanything.com you can configure all those email addresses to be forwarded to a specific email address.