A self-signed SSL certificate is an identity certificate signed by its own creator; however, they are considered to be less trustworthy.
Self-signed certificates cannot be revoked, which may allow an attacker who has already gained access to spoof an identity if a private key has been compromised. CA signed certificates (such as the ones provided by HostGator) have the ability to revoke a compromised certificate, which prevents further use.
Because of the security risk, we recommend that you purchase a secure SSL certificate, instead of using a self-signed certificate. On a VPS or dedicated server, you are welcome to install your own self-signed certificate, although we still do recommend that you install a CA signed certificate instead.