A CRT uses electrons fired at a phosphor-coated screen to display a pixel. An LCD panel uses intersecting lines of current to activate the liquid crystals at the junction. Modems convert digital signals into analog signals and transmit them over the phone lines. On the other end, a modem converts the analog signal back into a digital one for the computer to use. Full duplex is simultaneous bi-directional communication.
Half duplex is bi-directional communication while taking turns.
Floppy disk drives offer removable, rewritable, magnetic storage. Hard disk drives offer non-removable, rewritable, magnetic storage. A hard disk contains several distinct parts. Tracks are concentric circles of data on a given surface. Sectors are the wedge-shaped divisions of the disk.