understanding printer specs

ehrenfest

I'm a college students looking to buy a printer/scanner/copier combo. As I am very cheap, I am trying to understand the printer specifications in order to ensure that I buy the cheapest printer that has the features I want and as little else as possible.

I am leaning towards this one. I am trying to understand what specifications such as the following mean:

maximum black and white print resolution 600 x 600 dpi
maximum optimized color print resolution 4800 x 1200 dpi
maximum true color print resolution 4800 x 1200 dpi
maximum black and white copy resolution 600 x 1200 dpi
maximum color copy resolution 4800 x 1200 dpi
scanner optical resolution 1200 dpi
maximum scanner color depth 48-bit
maximum scanner resolution (interpolated) 1200 x 2400 dpi

Why are there two numbers for all of the resolutions except the "scanner optical resolution" ? Can someone explain what the first number and the second number means? Which of the different resolutions should I care about? What is the "maximum scanner color depth" ? Does anyone know of a good online guide for buying a printer that might explain this stuff?

Also, I can't find on the internet where it says what ink cartridges the printers take. Is it true that printers only take ink cartridges from the brand that made them i.e. HP printers can only use HP ink cartridges?