What is the difference between http and https?

HTTP stands for Hypertext Transfer Protocol. When you enter http:// in your address bar in front of the domain, it tells the browser to connect over HTTP. HTTP uses TCP (Transmission Control Protocol), generally over port 80, to send and receive data packets over the web. To put it simply it is a protocol that’s used by a client and server which allows you to communicate with other websites. 
Whereas HTTPS stands for Hypertext Transfer Protocol Secure (also referred to as HTTP over TLS or HTTP over SSL). When you enter https:// in your address bar in front of the domain, it tells the browser to connect over HTTPS. Generally sites running over HTTPS will have a redirect in place so even if you type in http:// it will redirect to deliver over a secured connection. HTTPS also uses TCP to send and receive data packets, but it does so over port 443, within a connection encrypted by Transport Layer Security (TLS).