Depending on the system you have purchased your actual HARDWARE may vary, but the following is a standard PC setup:-

Cased PC - Can be a TOWER or a DESKTOP case - This holds the Motherboard, Processor, Memory, Power supply, Hard Drive and Optical drive (Usually a DVD writer).

A Monitor - This is usually a flatscreen (TFT), though you may be using an older CRT (Looks like a television!). These vary in size but the most common sizes are 17inch, 19inch and 22inch.

A Keyboard and Mouse - needed to operate the PC. These may be WIRED or WIRELESS. The wired ones can be USB connected or the older PS2 system (A small, round 6 pin plug).