A patch bay is like a sonic traffic controller. It allows you to quickly route outboard effects into your signal chain. In other words, it a routing mechanism that will allow you to send audio signals from one place, to another via cables.
After you label and wire your patch bay, it will be easy for you to route audio signals that are outboard, without the hassle of moving and climbing behind your rack mounted gear or desk. This leads to a very ergonomically environment for the audio engineer. Patch bays are also very handy in tracking or tracing down problems in your signal chain or signal path and can give you options for a work around.
The most common type of patch bay that you will find in a recording studio is the TT or the 1/4 inch connectors. The TTis the tiny telephone type ones and is also called the Bantam. The holes in the TTs are 0.173 inches and these types of patch bays are usually found in the larger recording studios. The TT can have 96 jacks compared to the 1/4 inch patch bay, that can fit 32 to 48 jacks. So its a real space advantage to have the TT type patch bays. TT jacks can be wired as balanced. A balanced line offers common mode rejection and this mode cancels unwanted noise out. That said an unbalanced system can be noise free also, as long as you have quality calbes in addition to short cables.
Patch bays have front and back connection. The rear connections are permanent links to the gear it's connected to and the front jacks and are used for routing changes through the patch points.
Normaled patch bays are wired, so that a signal is routed internally from one permanent patch point to a predetermined permanent point without requiring a patch cable. In patch bays that are not normalled, or denormalled as some call it, all the signal routing is done in the front panel.
I hope this has opened your eyes up a bit more and helped you understand a bit more about patch bays. There is s much more to them, but it would take a book to explain it all.