Category 5 or better unshielded twisted pair, with all four pairs connected in a straight-through pinout configuration, is all you need.
Anything rated higher than Cat5 (for example, 5e, 6, 7) is tested to higher megahertz signaling levels; and may also have increased resistance to electromagnetic interference (EMI) and cross-talk due to a higher number of twists per foot/meter in the pairs. But the Gigabit Ethernet 1000BASE-T standard calls for minimum Cat5, and you're good out to 100 meters.
If you're under 100 meters and a cable tester doesn't certify the run as Cat5, and you're using all Cat5-rated components (cabling, connectors, jacks) and installation techniques, then it's time to start thinking about fiber, which is immune to EMI.
It doesn't hurt to have higher-rated copper, though. Think of it as insurance: good to have, but you probably won't need it.
Just don't wrap the cable around power transformers, UPSs, fluorescent lights, or elevator motors, and you'll be fine.
Hope this helps.
