The X.509 certificate extensions supported by this file are:
.CER – Certificate encoded in CER (Canonical Encoding Rules).
.DER – Certificate encoded in DER (Distinguished Encoding Rules).
.PEM – Base64 encoded certificate, enclosed between “–BEGIN CERTIFICATE–” and “–END CERTIFICATE–“.
.P7B – See .P7C as they are the same.
.P7C – PKCS#7 SignedData structure with no data, only certificate(s) or CRL(s). Public key only.
.PFX – See .P12 as they are the same.
.P12 – PKCS#12, can contain certificate(s) (public) and private key(s) (key protected).
PKCS #7: A standard for signing or encrypting data. A .P7C file is simply a SignedData structure, with no data to sign.
PKCS #12: Evolved from the PFX (Personal inFormation eXchange) standard and is used to exchange public and private objects within a file.
Finally, if we talk about x.509 certificate extensions, we have to mention the .PEM file that can contain certificates or private keys, enclosed between the appropriate BEGIN/END lines.