Fajr is the name of the dawn prayer that is performed by Muslims all over the world. It is 100% obligatory upon every Muslim as it is 1 of the 5 mandatory salah (prayer).
It can be performed from the moment of dawn but not after sunrise. For many people it is the time when people they wakeup and start their day. An natural & spirtual alarm clock that awaken them.
In a hadith reported by Jundub ibn Abdullah (May Allah be pleased with him), the Prophet ﷺ said,
“He who performs the Fajr will be under the protection of Allah.”
Source: Sahih Muslim, Book 5, Hadith 329
It can be difficult for some to wakeup early and pray Fajr but Muslims are known to sumit themselves to the will of Allah. In this there is a great reward for the believers.