Web, domains and email
CA
Abbreviation for Certification Authority
In short and in plain language
A CA is a body that gives out certificates for websites.
It shows that a safe link truly belongs to the domain.
Such bodies set rules with the firms that make browsers. One rule is how long a certificate is valid.
Definition
A CA is a certification authority that issues digital certificates for websites. It confirms that an encrypted 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 SSL certificates remain valid.