It's pretty well covered, but I'll take a shot at answering to learn the spirit of things here...
Ethernet is the most common local networking method; most often nowadays it uses cables which are buillt from a cabling wire meeting specifications for Category 5, 5e (enhanced) or 6, and with RJ-45 plugs on each end. So an ethernet cable you buy in the store or online will probably use Cat5, Cat5e or Cat6 wiring (nowadays mostly the latter two). Other varieties are much less common and we can ignore them.
These cables have 8 conductors and an easily used connector and they are cheaply available in many lengths and colors, so they have been "repurposed" for at least a dozen alternate uses in the DIY holiday lighting community. In those uses, the Cat5 (or whichever Cat) cable is not actually carrying ethernet networking, but it's the same kind of cable which COULD carry ethernet and was probably sold for that purpose. Thus we sometimes refer to it as a Cat5 cable to make clear that we are not using it for ethernet.
Cat5e and Cat6 are just upgraded speed-related specifications for 1 Gigabit ethernet; for our non-ethernet purposes however they are all the same, so you can get whatever's cheapest in that regard. (The quality of the connectors and jackets and the corrosion resistance of the contacts in them is more important to our uses than the 5 vs 6 differences). So if you see a description about using Cat5 (for non-ethernet), feel free to substitute 5e or 6 if it's handier.
As a note - since the came cable with the same connectors is used for so many different things, be careful to know what each cat5 (etc) cable carries what in your layout. It could be used to carry DMX, Renard, SSR data, Pixelnet backbone, and Pixelnet distribution (not to mention ethernet!) among several other uses; sometimes some of the conductors carry power which should not be misconnected. Imagine if in your home, your TV video, your audio, your speakers, your battery charger, and your computer mouse all uses pluggable cables with the same connectors - but each should only be used for for connecting jacks of the same purpose tho any would plug with any. That's what we have. So you may want to mark your Cat5 cables for how they are used.
In general for our purposes you will want stranded cable, which is more flexible and breaks less easily. Pre-made cables sold as "patch cables" will generally be stranded; solid conductors are mostly used in-wall and often created custom from large reels and crimp-on connectors. Stranded cable is even more important if your cable is carrying power on multiple strands (for example the Smartnet distribution cables between an active hub and a Smart String Controller) - if one strand breaks the others could overheat (which can be worse than just not working at all).
