Stands for Hypertext Transfer Protocol Secure , it is a variant of the web transfer protocol HTTP that adds a layer of security on the data in transit , it's a web resource protocol indicating that information is transferred over a secure connection.
HTTPS is an encrypted version that requires the use of a SSL certificate.
Seeing a website with https assures the user that the website is secure and any data (such as credit card information) they enter will only be recognised by your computer and the server and cannot be captured by an outside source.
It used to define how data is formatted and transmitted across the web. HTTPS has an advantage over HTTP in that the data sent when fetching a webpage is encrypted, adding a layer of security so that third parties can’t gather data about the webpage when the data is sent from the server to the browser.