Feeders are additional connections from your power wires to your track. I'm guessing you just have your DC power pack connected to your track at one spot, i.e. one wire goes to one rail, one wire to the other rail? A "feeder" would be another set of wires running from your power pack to another spot on your layout, where they connect to the track. You would then be supplying power to your track in two locations, and if there was a loose joiner or broken track between those two locations, you'd still be getting power to the whole layout.
Feeders are more critical in a DCC layout, where it's important to have a good, reliable digital signal throughout your entire layout. You'll see various recommendations for how many feeders to use, such as feeders every three feet, six feet, etc. Multiple feeders are not as critical in a DC layout--as long as the track is getting power, you're mostly good.
On larger layouts, the general practice is to have a track "bus" power line running beneath the layout. That's two wires carrying the current from your power source; every 3-6+ feet, you then have a small set of feeder wires going up from the track bus, through the plywood to connect with the track. Here's a picture of part of my layout (sorry it's the only one I could quickly find with an example of feeder wires). If you look carefully in the background underneath the trailers, you can see two sets of red and black wires coming up through the layout. Those are feeder wires connecting the track bus underneath to the upper level track, where they are soldered on.
You didn't mention how large your layout is. If it's fairly small, then you don't really need to worry about feeders. But if the far end of your track is...say 8-12' away or more, you could consider adding a set of power wires out to the far end. It would just be another set of wires running from your power pack, underneath the layout, and connecting to the track over there. Just make sure each wire is connected to the same rail as the wires on the close connection. I use colored wire to help tell the difference. Red goes to one rail, black goes to the other