Here is a great little chart comparing Category 5e and Category 6 Ethernet cables. It does a good job explaining the difference between capabilities of Cat 5e and Cat 6 cable.
Both cables look very similar from the outside, each will connect to an ethernet port, but they are different on the inside. If you aren’t sure what type of cables you have, look at the text printed on the cable — usually, it will tell you what kind of cable you have.
Now they even have Cat 7 and 8! Category 7 is best suited for use in data centers and large enterprise networks. While category 8is still in the development stage, will be able to support even faster transmission rates at greater distances.