Patchbays help you "patch" multiple effects in any order you want to mutliple sources (tracks/inputs...) without having to get behind the effects rack to re-route your cables.
Typically they have 20, 40, 48 or more channels with inputs and out puts on the back that route to the back of all your effects and to your mixing board and if you desire straight to you your recording device.
The front of your patchbay has inputs and outputs as well that let you put sa many effects in line and in any order you want by using easy to insert cable from the front of your rack.
The benifits: maximum flexibility with minimum effort. As Bruce indicated the more channels and effect combinations you have at your disposal the more this becomes a major time saver.
There are some tech tip archives at many websites listing the types (Normalled, 1/2 Normalled and Non-normalled) as well as types of cables they are designed for.
1/4 TS (Tips/Sleeve) non balanced cables.
1/8 TRS (Tip/Ring/Sleeve) balanced cables.
And some other more pro level balanced cables.
I'm pretty sure Musiciansfriend.com had a good Tech Tip about this in their archive.
I'm sure some one here has covered it in better detail also if you do a search on this forum.