PKCS #12 (PKCS12) is a format for storing cryptographic keys, certificates, and related objects. A single file may contain multiple objects. The file is often password-protected.
The format is also known as PFX (Personal Information Exchange). However, PFX sometimes refers instead to the the predecessor of PKCS12. Also, both PKCS12 and PFX are sometimes used as collective names for both formats.
PKCS12 was developed by RSA Security, based on the original Microsoft PFX format.