Witr (Hadith No. 803)


Volume 2, Book 16, Number 803:
Narrated Ibn Umar:
Once a person asked Allah's Apostle about the night prayer. Allah's Apostle replied, "The night prayer is offered as two Rakat followed by two Rakat and so on and if anyone is afraid of the approaching dawn (Fajr prayer) he should pray one Raka and this will be a Witr for all the Rakat which he has prayed before." Nafi' told that 'Abdullah bin 'Umar used to say Taslim between (the first) two Rakat and (the third) odd one in the Witr prayer, when he wanted to attend to a certain matter (during that interval between the Rakat).
Witr prayer is one of the greatest acts of worship that draw one closer to Allaah. Some of the scholars – the Hanafis – even thought that it is one of the obligatory prayers, but the correct view is that it is one of the confirmed Sunnahs (Sunnah mu’akkadah) which the Muslim should observe regularly and not neglect.
Imam Ahmad (may Allaah have mercy on him) said: Whoever neglects Witr is a bad man whose testimony should not be accepted. This indicates that Witr prayer is something that is confirmed. 

Night Prayer and Witr

Night prayer = Tahajjud = 2 + 2 + ... [+ 1 (witr)].
Shaykh Ibn Baaz (may Allaah have mercy on him) said: 
Witr is part of the night prayer, and it is Sunnah and it is the end of the night prayer, one rak’ah with which one concludes the night prayers at the end of the night, or in the middle of the night, or at the beginning of the night after ‘Isha’ prayer. You pray whatever you can, then you conclude it with one rak’ah. End quote.
Fataawa Ibn Baaz, 11/309
More on the difference between night prayer and witr here.
As for the if's and but's and how's etc., keep checking back. We'll be covering this topic called 'Witr' in detail iA.