Rick checks the certificate for the site he is viewing and sees that it reads *.example.com. What type of certificate is this, and why is it in use?

Wildcard certificates have a * in them, denoting that they can be used for any subdomain. For example, in this question, the wildcard would match any *.example.com subdomain like test.example.com and sales.example.com. Self-signed certificates will not link to a root or intermediate CA, and thus cannot be verified with CAs.