As long as the temperature was high enough, there was a balance between annihilation reactions of electrons and positrons and generation of electron-positron pairs.

After the temperature decreased a lot, much lower than the temperature where the protons and all the neutrons that had not decayed yet had combined into nuclei of helium and lithium, all the positrons annihilated with most of the electrons, so only a much smaller number of electrons survived.

After further cooling, most of the electrons became bound to nuclei, and all the matter became plasma, like most of the matter in the present universe still is (because most of the matter is inside the stars).

When electrons bind to nuclei, a plasma turns into a neutral gas, this happened in the recombination phase. The neutral gas then collapsed into stars which turned the gas making up the stars back into plasma. Also the energetic photons emitted by stars started turning the remaining gas back into a plasma which is called the reionization phase.

The earlier section says that the electromagnetic force didn't exist in its current form until 10*-12 seconds or so, when the electromagnetic and weak forces split from a combined "electroweak" force into their current forms.