In the ancient world the term parousia (“coming”) referred to a royal visitation. Any time a high-ranking dignitary, even Caesar himself, came for a visit everyone would gather outside and throw a big party and welcome him into their town.
There’s this great scene in the movie Gladiator where Commodus (Joaquin Phoenix) is entering Rome as the new head of the Empire. Pretorians and legionnaires are lined up, 50 deep, stemming the tide of surging onlookers.
That is a parousia.
The Second Coming of Christ is meant to be the ultimate welcome-back party for the King of Kings. In 1 Thessalonians Paul likened the return of our King as being like a splendid shock of might and love coming to us from Heaven.
It was the custom for significant members of society to go out and welcome the King at his parousia and then escort him back into their city. A parousia, then, did not entail the King leaving with the people and taking them somewhere else; but the people welcoming the King and bringing him back into their home.
What this means is that the Second Coming is not about removing Christians from the Earth, but about welcoming Jesus home to the New Heavens and the New Earth and the New Jerusalem.
Paul, like Jesus before him, believed that God had already begun the work of New Creation, occupying our world with the world to come. He likened it to a visiting Emperor being greeted, received, and then brought back home.
Here.