|Well it looks like your starting your homework research.|
There is a 16 bit 32, and 64. Imagine a bus that has 16 seats and 32 people to transport (people are bits of information) The bus will need to make 2 trips.
The I and O represent on and off switches. The language that a computer understans is made up of OIIOOIIOI 8bits plus 1 more for parity (error checking).
So... a few key words to google.
16,32,64 bit OS
16,32,64 bit bus.
I don't do homework either but a point in the right direction can be useful.