Hi all. New guy here.

I was replacing some receptacles in my home today and came across something new. The wiring was 14/3 but I thought nothing of it and just connected red and black to one side (hot) and neutral to the other. All seemed well. Went to reset the breakers (dual pole 15 amp) when I got a big flash inside the panel and no power was at the receptacles. It finally dawned on me and I removed the jumpers on all the plugs and all was well. Can someone explaing the theory as to why this happened?

Thanks

Half the plug is on a switch, half is hot all the time. There is a tiny metal tab between the two screws on the hot side that can be removed with needle nose. Then the red on one screw, black on the other after it's removed.

Sounds like a Multi circuit, a Red and Black on opposite phases sharing a neutral, turning on placed the red circuit on the black circuit, tripping the breaker.
See if you can find 2 breakers that remove power from the red circuit and the black circuit.