Fadak (فدك) was a garden oasis in Khaybar, a tract of land in northern Arabia; it is now part of Saudi Arabia. Situated approximately 140 km (87 mi) from Medina, Fadak was known for its water wells, dates, and handicrafts. When the Muslims defeated the people of Khaybar at the Battle of Khaybar; the oasis of Fadak was part of the bounty given to the Prophet Muhammad, who gifted it to his daughter, Fatimah.
Based on the information that I have come across, the wives of the Prophet (s) did not receive an inheritance from his estate, but rather were given a 'provision' or stipend. This was either left for them in the lifetime of the Prophet (s) or was given by Abu Bakr as the first defacto caliph.
So were the wives not entitled to any inheritance? There is an interesting narration in the Mu'jam al-Buldan of Yaqut al-Hamawi that after the demise of the Prophet (s) the wives considered sending 'Uthman (presumably bin 'Affan) to Abu Bakr as their representative to demand their eighth share. But 'Aisha, the daughter of Abu Bakr and one of the wives of the Prophet (s), opposed it and all the wives withdrew from such a demand.
This is important because had the wives been entertained in their claim for inheritance, then Lady Fatima's (a) claim to Fadak could not have been refuted on the grounds that the Prophets do not leave heirs as was claimed by the first caliph Abu Bakr.
Fadak, in any case, was a lifetime gift that the Prophet (s) had made to Fatima (a). That estate was not handed over to her by Abu Bakr despite her claims to it. This is widely documented in the hadith and historical sources.
For more details on the estate of Fadak and the politics that was at play behind it being withheld from Fatima (a) please refer to: