Web, domains and email
CA
Abbreviation for Certification Authority
In short and in plain language
A CA is a body that issues digital certificates.
You need them for encrypted links to websites. The body confirms that a link really belongs to the domain.
Such bodies set rules with the firms that make browsers. One rule is how long a certificate stays valid.
Definition
A CA is a certification authority that issues digital certificates for encrypted connections to websites. It confirms that a connection really belongs to the stated domain. In the CA/Browser Forum, these authorities and browser makers jointly set rules, for example on how long certificates remain valid.