SSL / TLS
Transport Layer Security (TLS) is the cryptographic protocol that powers HTTPS. "SSL" is the deprecated predecessor — when people say "SSL" today they almost always mean TLS.
Related terms
TLS 1.2 vs TLS 1.3
TLS 1.3 (2018) is faster (one round-trip handshake) and more secure (removed legacy ciphers) than TLS 1.2.
TLS Certificate (Leaf, Intermediate, Root CA)
An X.509 certificate is a signed document binding a public key to a domain.
Certificate Chain
The sequence of certificates linking your server's leaf cert back to a trusted root CA.
Wildcard Certificate
A TLS cert valid for one subdomain level — `*.example.com` covers `api.example.com` but NOT `v2.api.example…
Let's Encrypt
A free, automated, non-profit Certificate Authority issuing 90-day TLS certificates.
HSTS (HTTP Strict Transport Security)
An HTTP response header that tells browsers to only ever connect to your site over HTTPS — protects against…