TLS Encryption (HTTPS)
TLS encryption (Transport Layer Security, visible as HTTPS) encrypts the data transfer between browser and web server, so that third parties cannot read transmitted content such as form entries or login credentials.
In practice
HTTPS is a basic requirement today: browsers actively mark unencrypted HTTP websites as "not secure", and Google has used HTTPS for years as a light but real ranking signal. A valid TLS certificate can now be set up free of charge and automatically with most hosting providers.