What is Hajj?

إِنَّ أَوَّلَ بَيۡتٖ وُضِعَ لِلنَّاسِ لَلَّذِي بِبَكَّةَ مُبَارَكٗا وَهُدٗى لِّلۡعَٰلَمِينَ ﴿٩٦﴾ فِيهِ ءَايَٰتُۢ بَيِّنَٰتٞ مَّقَامُ إِبۡرَٰهِيمَۖ وَمَن دَخَلَهُۥ كَانَ ءَامِنٗاۗ وَلِلَّهِ عَلَى ٱلنَّاسِ حِجُّ ٱلۡبَيۡتِ مَنِ ٱسۡتَطَاعَ إِلَيۡهِ سَبِيلٗاۚ وَمَن كَفَرَ فَإِنَّ ٱللَّهَ غَنِيٌّ عَنِ ٱلۡعَٰلَمِينَ ﴿٩٧﴾

Indeed, the first House [of worship] established for mankind was that at Bakkah [i.e., Makkah] - blessed and a guidance for the worlds. In it are clear signs [such as] the standing place of Abraham. And whoever enters it [i.e., the Ḥaram] shall be safe. And [due] to Allāh from the people is a pilgrimage to the House - for whoever is able to find thereto a way. But whoever disbelieves [i.e., refuses] - then indeed, Allāh is free from need of the worlds.

وَأَذِّن فِي ٱلنَّاسِ بِٱلۡحَجِّ يَأۡتُوكَ رِجَالٗا وَعَلَىٰ كُلِّ ضَامِرٖ يَأۡتِينَ مِن كُلِّ فَجٍّ عَمِيقٖ ﴿٢٧﴾

And proclaim to the people the ḥajj [pilgrimage]; they will come to you on foot and on every lean camel; they will come from every distant pass -