certificate
termcryptographysecurity
A signed statement binding a public key to a name, valid for a period, issued by an authority the relying party has decided to trust.
Three things fail here and they fail differently. The name may not match what the client asked for. The period may have ended, which is the outage that arrives on a date somebody could have read a year in advance. Or the chain may not lead to a trusted root on that particular machine, which is why a certificate that works in a browser can fail from a server with an older trust store. Nothing about a valid certificate says the operator is honest - only that an authority attested to a name.
Also known as: x509, tls certificate