via：https://www.techadvisor.co.uk/buying-advice/network-wifi/best-ethernet-cables-in-2018-3671060/

As you might have guessed, higher numbers tend to mean faster speeds. Cat5e is rated for 1Gbps and bandwidths of 100MHz, Cat6 offers up to 10Gbps at up to 250MHz bandwidth, and Cat7 can go as high as 100Gbps with bandwidths up to 600 MHz.
The other major difference is that Cat7 cables are always shielded, which helps reduce interference and crosstalk. Cat6 cables are sometimes shielded, though retailers often aren’t clear when they are and aren’t, and Cat5e cables never have shielding.
Since most ethernet cables are fairly cheap, there’s an argument for buying Cat7 cables - especially for shorter (and thus cheaper) cables. However, most users won’t see any real speed benefits from Cat7, so Cat6 is probably the sweet spot for most - unless you want to be certain you’re future-proofing your cabling.
Length
Alongside category, length is the next most important element of an ethernet cable. Partly that’s obviously just a question of how far you need the cable to reach, but it also relates to speed and performance.


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