SSL (HTTPS) encrypts the connection between a visitor’s browser and your site. Modern browsers expect it — without it, visitors see warnings that hurt trust and conversions.
What you usually need
Most small business sites need a standard domain-validated certificate covering the live hostname (and www if you use it). Higher-assurance certificates exist for organizations that need them.
When something looks wrong
Check that the certificate matches the exact domain, has not expired, and that the site is not loading insecure scripts over HTTP. After a fix, clear CDN or site caches. For a live outage, open Get support rather than troubleshooting passwords in chat.