A printer is a piece of hardware that will print computer information onto paper. This is distinct from multitasking. Advertisers often use megahertz numbers as a means of showing a processor's speed. A program is a series of instructions for a computer, telling it what to do or how to behave. It is however different from an applet.
Program is also the verb that means to create a program, and a programmer is one who programs.
Loosely speaking, parallel implies a situation where multiple things can be done simultaneously, like having multiple check-out lines each serving people all at once. Parallel connections are by their nature more expensive than serial ones, but usually faster. Also, in a related use of the word, often multitasking computers are said to be capable of running multiple programs in parallel. Sometimes due to hardware limitations, disks have to be divided into smaller pieces. These pieces are called partitions.