PEM: (*.crt) PEM Text format with headers
PEM chain: (*.pem) Concatenated text format of the complete certificate chain in one PEM file
PEM + key: (*.pem) Concatenation of the certificate and the unencrypted private key in one PEM file
PEM + PKCS#8: (*.pem) Concatenation of the certificate and the encrypted private key in PKCS#8 format in one file