This is in reference to modem communications.
A half-duplex system allows communications in both directions, but only one direction at a time (not simultaneously). Any radio system where you must use "Over" to indicate the end of transmission, or any other procedure to ensure that only one party broadcasts at a time would be a half-duplex system.

A good analogy for a half-duplex system would be a one lane road with traffic controllers at each end. Traffic can flow in both directions, but only one direction at a time with this being regulated by the controllers. Another analogy is a walkie-talkie format as mentioned above to be "Over".

A single request from a Web browser for a single item from a Web server. When a browser displays a Web page that contains 2 graphics, 3 hits occur at the server: 1 hit for the HTML page itself, plus a hit for each of the two graphics.

The main page of a Web site.

A computer attached directly to the Internet. Users on client machines can connect to hosts to transfer information.

A hotspot is a place where computers with wireless cards can pick up a network signal and get broadband Internet access.

stands for Hypertext Transfer Protocol. It is a set of rules for transferring data that dictates to your server which website you want to view or download.