All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
Baytul-Maqdis is itself the Al-Aqsa mosque about which Allaah Says (what means): {Exalted is He who took His Servant [i.e. Prophet Muhammad () by night from al-Masjid al-Haram to al-Masjid al-Aqsa, whose surroundings We have blessed, to show him of Our signs. Indeed, He is the Hearing, the Seeing.}[Quran 17:1] It is also confirmed that the Prophet said: "When the tribe of Quraysh belied me, I stood on the Hijr of Isma’eel (Ishmael) [The area adjacent to the northwest side of the Ka’bah, enclosed by a low semi-circular wall in the sacred mosque in Makkah] and Allaah showed me Baytul-Maqdis and I started describing it to them while I was looking at it."
This is the meaning in principle, however, sometimes we mention Baytul-Maqdis to refer to something greater than it. Hence, some times it refers to the area in which Baytul-Maqdis and its precincts are, as in the saying of the Prophet said: “Baytul-Maqdis will be conquered.”
It is also used to refer to Jerusalem which includes Al-Aqsa mosque in the general meaning. However, by Baytul-Maqdis we do not refer to the entire Palestine or Greater Syria, and these are not considered holy as Baytul-Maqdis, however, it may be included in the surrounding area of Al-Aqsa that has this characteristic (i.e. sanctity). Allaah Says (what means): {Exalted is He who took His Servant [i.e. Prophet Muhammad ()] by night from al-Masjid al-Haram to al-Masjid al-Aqsa, whose surroundings We have blessed, to show him of Our signs. Indeed, He is the Hearing, the Seeing.}[Quran 17:1]
Allaah Knows best.