SSL Glossary

CSR / PKCS#10 / P10 / request
This is the public portion of a keypair. It includes the public RSA key, plus some metadata about the final certificate. Once a request is signed it becomes a certificate.
CRT / certificate / PKCS#7
This is a certificate, which means it is a request which has been signed by a certificate authority. Like a request, it contains the public key of the key pair.
PKCS#12 / P12
A file format for storying an encrypted key, it's certificate, and optionally the certificate chain. Private key is required.
The private key of a keypair. While the word "key" can refer to either the private key or the public key, generally within X509 and SSL, key refers to the private key specifically.
A public and private key. The public key is usually in the form of a request or certificate.
certificate authority / CA
An entity that signs CSRs, thus making them into CRTs. Technically speaking, a CA is just a certificate used to sign CSRs. This CA certificate is generally trusted by all relevant parties. CAs are often, but not always, self-signed.
certificate revocation list / CRL
This is a list of certificates that have been revoked by a CA. It must be signed by the CA to be valid.
CRL distribution point
This is the URI where a CRL can be retrieve. Should not be protected by SSL
self-signed / root certificate
A certificate whose signer is itself.