Certificates
Certificates are used to create secure communication between clients and servers. Users can purchase certificates from a certificate authority (CA-signed certificates) or they can use self-signed certificates.
Self-Signed Certificates
Self-signed certificates (as the name implies) are signed by the same entity whose identity they certify, as opposed to being signed by a certificate authority. Self-signed certificates are not considered to be as secure as CA certificates, but they are used by default in many applications.