A PFX file, or Personal Information Exchange file, is a password-protected file certificate that is commonly used for code signing applications and securing SSL certificates. It is a collection of cryptographic keys, digital certificates, and intermediate authority certificates that help to strengthen an applications security. The PFX file format is derived from the PKCS 12 archive file format certificate, and it stores multiple cryptographic objects within a single file, including X.509 public key certificates, X.509 private keys, and X.509 CRLs.

To create a PFX file, you can use tools like Advanced Installer or PowerShell commandlets. The process involves exporting a certificate and private key, defining where the PFX file will be stored, and validating the information. PFX files can be used to sign code, secure SSL certificates, and store important cryptographic assets in a password-protected bundle.

In contrast, a .cer file is a certificate stored in the X.509 standard format that contains information about the certificates owner and public keys, but not private keys. A .cer file can be used to verify the authenticity of a certificate, but it cannot be used to sign code or secure SSL certificates like a PFX file can.