A public-key certificate managed by the highest authority (untrusted authority, Root CA) that issues certificates or self-signed certificate. In general, the public key of a trusted Root CA (Verisign, Geotrust, etc.) is embedded in the OS, and through that public key, it is checked whether the certificate used by the web server is a trusted Read more about What is the Root CA Certificate?[…]

It is a kind of electronic identification card and electronic seal created by adding the owner’s information to the public key required for verification of the electronic signature. These certificates are used to encrypt the communication between the user and the webserver to increase the security of the website.