There are many different models and brand names but they all work basically the same, gas is connected to the stove and different components distribute the gas to different part of the stove.
They are two major differences in lighting the stove automatically, one is with a glow bar, the other is with ignition, these components are both igniters the difference is one glows and draws a certain amount of current then it opens a valve that let the gas out to the oven burner then it lights the gas, if this igniter is defective it might glow but will not open the valve as it is not drawing enough amperage, other times it will not glow because it is burnt out, sometimes it will open the valve but because it is not shining full power the gas will build up in the oven and you will smell gas because it is not lighting the gas.
If you put food in the oven and set the thermostat to 3.50, or 400 degrees and after an hour when you check the food it is still cold and you can see there is an orange glow coming from the bottom of your oven that is an indication that your igniter is defective.
The other type of oven use the spark igniter, both kinds of stove use spark igniter for the top burners, the spark igniter oven when you turn it on the thermostat send a pilot flame to the oven, the micro switch on the thermostat also send a spark to ignite the pilot through a spark module.