Certificate or Asymmetric Key?

One of the first questions regarding the security objects in SQL Server is what is the difference between certificates and asymmetric keys.

Similarily, certificates and asymmetric keys both encapsulate RSA keys. Certificates offer more flexibility, in that they may be imported from external sources. For example, a .CER file. Once the certificate or asymmetric key is available from within the database, the range of implementation options is essentially the same.