THE MEANING AND SIGNIFICANCE OF HAJJ
Hajj means pilgrimage to makkah which is performed in obedience to Allah's commandment in Qura'an (22:27, 3:93). It's a dyuty at least once in a lifetime for a who are able, physically and financially to do it.
sourced image
The significance of the 🕋 ka'aba and the hajj is mentioned in the following verse if the Qura'an;

spiritual objectives of Hajj

The Hajj is a great experience for a Muslim. He leaves his home to his family and friends and his familiar surroundings and travel to the center of Islamic worship, the place towards which he has turned in prayer so many times. Here at last he's to face to face with the ka'aba. He may recall its ancient history, remembering prophet Ibrahim, his wife hajara and his son prophet Ismail. He may recall how the ka'aba was for centuries defiled by the idol-worshipper and at last purified and restored to the worship of one God at the time of prophet Muhammad(phuh). He may recalled the struggles and suffering endured by the first Muslim and final success with the destruction of the idols and conversion of makkah and Arabia to Islam. He may also reflect on how Islam spread from this place to his own country and to the rest of the world.
As he looks around him, he sees people grok every land, every race and every color, of different social, economics and educational level, representing all mankind at this great yearly gathering to perform the acts of worship which makes up the Hajj.

This aspects of the great assembly of mankind is demonstrated with even greater emphasis at Arafat, where millions of people stand throughout the afternoon in the wide plain to celebrate Allah's praise and seek for his forgiveness and mercy. The occasion reminds muslim of the forthcoming assembly of the day of judgment when all human beings will stand equal before Allah to know their rewards or punishment.
Throughout the day of the hajj, the pilgrim is cut off from his normal routine of life. He dresses like everyone else in the simple unsewn uniform of hajj and enters the state of ihram(consecration). He joins the crowd going to ka'aba. He traces the footstep of hajara in hastening between the hills of safa and marwa. He makes his sacrifice in obedience to Allah. He goes daily to stone the jumrat(pillar( representing his rejection of shaitan.
The rest of his time is spent in prayer, meditation and reading if the Qura'an, full of hope for Allah's forgiveness and blessings. Indeed it's a great spiritual experience for those who go with sincere intention.

the spiritual objectives of hajj may therefore be summarized as ;

purification of the soul

forgiveness of sins

wholehearted worship in obedience to Allah and seeking Allah's pleasure and reward, which may come in any form, in this world