Here are some common certificate file extensions:
.crt: Includes private keys and allows enabling SSL/TLS encryption
.cer: Contains just public keys and enables authentication
.p12: A combined certificate and key file that supports storage of private and public keys
.pfx: A combined certificate and key file that supports storage of private and public keys
.pem: A combined certificate and key file
.ca-bundle: A certificate file extension
.p7b: A certificate file extension
.p7c: A certificate file extension
.p7s: A certificate file extension
Certificate extensions are information fields that provide additional information about the certificate.