What's the difference between SSL and TLS?

SSL (Secure Sockets Layer) was the original protocol, now deprecated and insecure. TLS (Transport Layer Security) is its successor — TLS 1.2 and 1.3 are the current secure versions. The term ‘SSL certificate’ persists for historical reasons; every modern ‘SSL certificate’ is actually used with TLS. SSL 3.0, TLS 1.0, and TLS 1.1 are all deprecated and should be disabled.