As the category number gets higher, so does the speed and Mhz of the wire. This is not a coincidence, because each category brings more stringent testing for eliminating crosstalk (XT) and adding isolation between the wires.
This does not mean your experiences have been the same. Physically you can use Cat-5 cable for 1 Gb speeds, and I have personally used cable longer than 100 meters, but because the standard has not been tested for it, you'll probably have mixed results. Just because you have Cat-6 cable, doesn't mean you have 1 Gb network speeds either. Every connection in your network needs to support the 1 Gb speed and in some cases, the connection will need to be told in software to use the available speed.
Category 5 cable was revised, and mostly replaced with, Category 5 Enhanced (Cat-5e) cable which did not change anything physically in the cable, but instead applied more stringent testing standards for crosstalk.
Category 6 was revised with Augmented Category 6 (Cat-6a) which provided testing for 500 Mhz communication (compared to Cat-6's 250 Mhz). The higher communication frequency eliminated alien crosstalk (AXT) which allows for longer range at 10 Gb/s .
Factory Common production specifications:(PAST 90m Fluke TEST)
6.3*2.5mm(U/UTP Self Support)
Mainly used in the wiring system betweenwork area correspondence leading-out terminal and distribution wiring frames connection.As well as used in the housing synthesis wiring system between user correspondence leading out terminal and patch pannel.