ignitor

What does the ignitor do? It is the only thing i have not replaced on my 89 Tercel 5 speed? The car stalls bad when going threw the gears. I have rebuilt the carberator replaced plugs,wires,cap& button, fuel & air filter,o2 sensor and the fuel pump. I thought i had it fixed last week when i replaced the coil, but today it started doing it again,no power at all until you slow down. The ignitor is tied into the distributor,so what does it do? If the ignitor is bad did i ruin the coil?

Thanks