Difference between types of wires:

I’m trying to implement a little network, we’re changing offices.

When I ty to purchase the wire to do so, they tell me there are at least two types.

I want to know:

1. What is the difference between UTEP Level 3 wire and another which is level 5.

2. Which is the best option to connect a small office (8 pc’s at most).

3. Is there any other option available which suits me best and why?

I hate to say this but it’s urgent!!!