The difference between HTTPS and HTTP lies in the inclusion of SSL/TLS encryption in HTTPS. HTTP (Hypertext Transfer Protocol) transmits data in plain text, which can be intercepted by malicious entities. In contrast, HTTPS (HTTP Secure) encrypts the data exchanged between the user's browser and the server, providing a secure connection and ensuring confidentiality and integrity of the transmitted information. This security is crucial for online transactions and protecting sensitive user data.