Welcome to Macrumors!
Firstly, what you have to understand is the basics about Mac and Windows.
Mac is an Operating System from Apple and Windows is an operting system from Microsoft - the two companies are IT giants and sell many many computers with their own OS installed.
A 'PC' is a general term for any non-Mac computer - but more commonly a PC is reffered to as a larger tower machine running Windows. A tower machine is usually sold with a monitor screen, a keyboard, mouse and set of speakers.
A 'PC' laptop is a laptop which is a smaller single piece 'all in one' machine which is a keyboard, with a swing shutting screen running Windows also.
An iMac is similar to a windows PC tower except everything is built in to thw back of the screen rather than in a large tower shaped machine.
A Macbook (mac laptop) is exactly the same as a PC laptop except for the design and the fact that it runs Mac OS.
Microsoft sell Windows into a lot of different makes of machine for example Acer, Dell, HP etc whereas Apple build Mac OS into ONLY Apple products, meaning you can get Windows on machines built by ANY manufacturer and you an only get Mac OS from an Apple store, on an Apple machine.
Hope this insight helped.
S