Most stars burn steadily and if we could see them from space they would not actually be twinkling at all.
As the light from a star passes through the Earth’s atmosphere, it is bent by changes in the air temperature. This makes the light appear to flicker. Because of this effect observatories for studying the stars are situated on the mountain-tops. The reason for this is because the higher up you go, the air becomes thinner and it is less likely to cause the twinkling effect.
Sometimes a giant star explodes and is blown to pieces. This is called a supernova. A supernova explosion sometimes results in a pulsar. A pulsar is a rapidly spinning star that gives off pulses of radio waves.