TCP/IP is a transport layer protocol. HTTP is an Application layer protocol in the OSI model.
Uniform Resource Locator. This is the website name that a DNS has mapped to an IP address for the server hosting the web page.
This is the idea that clients(your PC) establish a session with a Server(webpage). Upon request from the client, the server will deliver the neccessary files for the client to use. This session is established using handshakes to acknowledge a link between the two machines.