Salah is one of the core components of the Islamic ideology. A prayer is generally a means of remembrance of Allah SWT, and getting His mercy and blessings. It is of two types: first is the obligatory Namaz, which is to be offered five times a day at specific times with no choice of skipping it under normal circumstances, while second is the Nafl (supererogatory prayer) which is optional and one is not answerable to the Almighty for not performing it.

“Nafl” is an Arabic word, which means “to get something extra”. There are many kinds of non obligatory supplications such as Tahayiat-ul-wudu (offering two raka`ts right after ablution), Ishraak (after Fajr, praising the Lord through Tasbeeh till the Sun has risen, then performing two or four raka`ts), Chaasht (carrying out at least two raka`ts when the Sun has set high), and Tahajjud (praying in the later part of night) etc. The last one has been even emphasized to be executed in the Holy Quran:
Fazail E Tahajjud
How Many Rakat in Tahajjud Namaz
Tahajjud Namaz Ki Fazilat
Namaz E Tahajjud Ki Fazilat in Urdu
Power of Tahajjud
Tahajjud K Fazail in Urdu
Benefits of Tahajjud Dua
Rewards of Tahajjud Prayer