What a certificate does
TLS certificates help a browser verify the identity associated with a site and establish an encrypted connection. They do not certify that a company is trustworthy or that every part of a site is secure.
Certificate types and validation
Domain validation confirms control of a domain using a specified method. Other validation levels may check organizational details. The right type depends on the use case and what the issuing authority requires.
Renewal is part of security
Certificates have validity periods and must be renewed or automatically replaced before expiry. Confirm who owns renewal, how failures are reported, and whether all hostnames are covered.
Check the whole path
HTTPS requires the certificate and the site configuration to work together. Review redirects, mixed content, application cookies, and any proxy or CDN settings that affect TLS termination.