A catch all email address will receive all emails sent to a specific domain name. For example if your email address is email@example.com and someone sent an email to firstname.lastname@example.org, even though that the email address is spelt wrong, the email will be received by the catchall email address.
This can be of benefit, however if you choose to accept all emails being sent to your domain it can potentially open the gates for spam attacks and other problems could occur. It will also use up extra resources or the server which will make performance generally slower for things like loading webpages.
Please get in touch with our support team if you require further assistance.