Lo-Z is for low impedance sources (generally balanced, like microphones).
Hi-Z is for high impedance sources (like guitars)

If you have any ground loop problems or have long cable runs, good advice would be to make all your connections balanced and shielded. This eliminates a lot of distance-induced noise, RFI etc.

To expand on what Codemonkey said - it's not the cables that are Lo or Hi Z, it is the sources and the jacks they plug into. Lo-Z usually connects with a 3-conductor XLR connection. Hi-Z with a 2-conductor 1/4 inch connection.

As far as quality of cables go, the most important difference is in durability. Cheap cables break all the time and the breaks are intermittent and sometimes hard to detect. Moving up to at least mid level cables like pro-co saves a ton of hassle. There are several regular posters on this board who make excellent cables for reasonable prices. I've bought a bunch from Jeremy Cucco that I've been very pleased with.

A lot of people believe that there are differences in sound between even high quality cables. Whatever the truth in this, the differences are subtle enough that there is still a lot of debate about this after a lot of careful listening tests. The differences are probably impossible to detect on budget gear.

cables is a more complicated subject
but
for audio and for the typical distances in the average project studio cables should be as simple as two or three cable types

as Bob said durability for the cables on the studio floor is a big issue
good RF and noise handling is important
good size and solderability of the connection points
and
IF you Krone then the cable size needs to be right

then there is the multicore .. if you want to go that way for effects racks etc

I like the Star Quad for the mics (double shield)
foil with a drain wire for the line levels
and similar for the multicores
the foiled stuff is not for bending and walking on every day

for the small studio I tend not to multi cores for the mics
but you can get Star Quad in multicore form

cables do have impedance and capacitance
... I don't want to confuse the thread and we can look at that discussion elsewhere

Thank you all for the clarification! :) I will probably look into a couple durable cables.