DER and PEM formats

encoding (also for extension) . Der = Extension der is used for binary DER-encoded certificates. These certificates can also be extended with a CER or CRT. The more appropriate term is "I have a DER-encoded certificate" instead of "I have a der Certificate". PEM = extension PEM for ASCII (BASE64) encoding of various V3 certificates. The file begins with a line of "-–begin ...".
Der Type is not encoded decoding, directly binary data can be directly used; PEM type data to be decoded according to Base64 encoding, the resulting data needs to be added or clipped special characters-, \ n, \ r, begin information, end information and so on.