There is only one file type that uses the .P7C extension:
PKCS #7 Certificate File
Digital certificate file used by various applications to authenticate a Web identity; similar to a .P7B file, both of which contain a public key used to verify an entity using public-key cryptography.
Once a P7C file has been imported in a program, the software typically places the verified entity on its trust list.
Updated: March 2, 2019