SSL Certificate

RSA

x.509

Format of public key certificate standard. Contains public key along with other information depicting the issuer etc.,

DER

Binary encoding format to store data, not only x.509 but also PKCS8 in file. The result can not be viewed in text editor as it is binary

PKCS8, PKCS12

Standard syntax for persisting private key information.
It is typically exchanged by using PEM encoding format

PEM

Base encoding of DER certificate, can also encode others like private and public key etc.,

-----BEGIN PUBLIC KEY-----
...Base64 encoding of the DER encoded certificate...
-----END PUBLIC KEY-----

Usually begin with -----BEGIN and end with -----END