RedHat provides an extensive explanation of certificates, what they are, and how they authenticate web sites, servers, clients, or people.
The Linux Documentation Project provides a “how to” about SSL certificates.
SSL/TLS uses public-key certificates to authenticate web sites.
Video notes: cys.me/vid/c11
Video #12 explains the digital signature process vimeo.com/208191369
The previous video explains SSL/TLS using the RSA public-key cipher vimeo.com/202087967
See the entire Cryptosmith series in its album vimeo.com/album/4229550