PKE keys vs. digital certificates

Question

I am trying to understand the difference between PKE keys (public and private) and digital certificates, such as SSL certs.

• Do SSL certs contains keys inside them? If so, which ones (public or private)?
• If so, why is it necessary for the SSL cert to contain the key(s)?
• Is there a notion of "public" vs "private" certificates like there is with keys?

Answer 1

A digital certificate "contains" a public key, along with some other information. The other information often includes a host name, and the certificate may be digitally "signed" by certificating authority. Digital certificates do not contain private keys.

Certificates contain public keys because the purpose of the certificate includes providing the public key to clients.

Since certificates don't contain private keys, there is no notion of "public" versus "private" certificates.