All matter and all radiation were compressed together, and conditions were so extreme that one could become the other. A photon could become matter, and vice versa. Matter and radiation were coupled together. We can only recreate this in laboratories now, no longer see it in the universe. There was also more antimatter back then, something else than we can create in the lab, but only see rarely now in the universe.
Electrons have anti-electrons, which have positive charges.
In extreme conditions, two very high energy photons colliding together can knock themselves into becoming an electron and anti-electron pair. Earliest is called Planck era . Beyond the limits of what we can understand. The whole universe was the size of a nucleus of an atom. The electroweak era is when the weak and electromagnetic force were still bound together and ended at 10 -10 seconds.