I always visualized that the tidal locking to be sort of like meshed gears, such that the one revolution around itself is same as a rotation around the star/planet if its a satellite.
But that shouldn't affect the day/night in this case right? Since we are talking about planets not satellites of planets and they are light sources not just reflecting light from the star. Can you please correct where I am wrong?
Tidal locking means that the denser side of the lighter body always faces the heavier body, and the less-dense side of the lighter body already faces away from the heavier one.
The moon is tidally locked to the Earth, which is why it has a dark side.
It follows from "one revolution around itself is same as a rotation around the star" that a planet tidally locked to its star presents the same face to the star at all times, so you have a 'Day' side and a 'Night' side. Neither side of which is likely to be particularly life friendly. Perhaps there might be some 'twilight zone' that could be though...
But that shouldn't affect the day/night in this case right? Since we are talking about planets not satellites of planets and they are light sources not just reflecting light from the star. Can you please correct where I am wrong?