A TLS certificate binds a public key to a server name and helps establish a protected HTTPS connection. For Joomla, it is normally installed on the web server, reverse proxy or hosting platform.
Browser verification
The browser checks the website name, validity period and chain of trust. A certificate for one name does not necessarily cover another. The matching private key must remain secret.
The familiar term “SSL certificate” persists, but modern secure connections use TLS. A certificate does not prove that the operator is trustworthy or fix application vulnerabilities.
HTTPS for Joomla
First make HTTPS work on the server, then coordinate Joomla settings and redirects. Check for loops and mixed content, where a secure page requests resources over HTTP.
After configuring Joomla, test login, forms, files and language versions. Certificates require renewal, and automated renewal needs monitoring. With a proxy, check where TLS terminates and how the remaining request path is protected.
Conclusion
A TLS certificate is part of connection security. Reliable HTTPS depends on correct names, a trusted chain, timely renewal and checks of the whole website.