Wajib prayers are the ones not mentioned in the Quran, but indicated to be obligatory according to the Sunnah of the Prophet.
These are prayers that seemed Fard according to how much emphasis the Prophet put on them, and are considered Fard (obligatory) by some schools of thought. Others believe that they are Sunnah. It’s best to think of them as higher in importance than Sunnah but one step below the Fard (5 daily prayers, Jumah and Janazah) that are mentioned in the Quran.
Witr is performed after the salah of Isha’a (dusk). It may contain any odd number of raka’ah from one to eleven according to the different schools of jurisprudence. However, Witr is most commonly offered with three raka’ah.
To end prayers for the night after isha’a, the odd numbered raka’ah must have the niyyah of “wajib-ul-Lail”, which is mandatory to “close” one’s Salah for that day.
Eid Salah is performed on the morning of Eid ul-Fitr and Eid ul-Adha. The Eid prayer is most likely an individual obligation (fard al-ayn), though some Islamic scholars argue it is only a collective obligation (fard al-kifayah). It consists of two raka’at, with seven takbirs offered before the start of the first raka’ah and five before the second. After the Salah is completed, a sermon (khutbah) is offered. However, the khutbah is not an integral part of the Eid Salah. The Eid Salah must be offered between sunrise and true noon i.e. between the time periods for Fajr and Zohr.