Question

What do you understand by dawn and twilight? Explain.

Answer 1

Dawn is the time that marks the beginning of twilight before sunrise.Twilight is the time between dawn and sunrise, or between sunset and dusk

Answer 2

twilight is the period between dawn and sunrise, or between sunset and dusk, when light is still visible in the sky due to sunlight scattering off the atmosphere.the sun itself is not directly visible because it is below the horizon. 
dawn occurs before sunrise, before the top of the Sun reaches the horizon.it is recognized by the presence of weak sunlight, while the sun itself is still below the horizon.