What a TLS certificate tells you
A certificate binds a public key to a domain name. Your browser checks the name, the expiry date and the chain of trust before it opens an encrypted connection. Keeping certificates current is part of running a website.
Why latency varies
Physical distance is only one part of a request. Routing, network congestion and server processing all contribute to its round-trip time. A useful measurement compares repeated requests over the same path.