Transport Layer Security (TLS)
The S in HTTPS. Privacy and integrity for data on the wire. Certificates you actually manage.
TLS is the widely used protocol that protects confidentiality and integrity of internet traffic. HTTPS is HTTP plus that layer. Old SSL is retired language and retired crypto.
Use current versions and cipher suites, rotate certificates, and turn on HSTS where it fits. A padlock on a phishing site still encrypts the theft.
Fact source: ASD's ACSC glossary.