The “true” dawn refers to the time of merit for the fajr prayer; the “false” dawn refers to the time when the night has come to an end and for the first time, a white light comes into the horizon in the east of the sky which resembles the ear of a wolf. At this moment, although the night has ended, but it still isn't time for the fajr prayer (it hasn’t officially become dawn yet). This is why this time is referred to as the “false” dawn. As time passes, the white light spreads and fills the east of the sky, making it the time for the fajr prayer (at this time it has officially become dawn). This is why this time of day is called the “true” dawn.[1]

In a nutshell, there are three main differences between the two:

1) The “false” dawn is away from the horizon, while the “true” one is attached to it.

2) The false dawn is vertical, while the true one is horizontal.

3) Right when it breaks out, the false dawn is bright and perishes as time passes, while the true dawn begins with a weak light and gradually grows as time goes on.[2]