Jehovah's witnesses believe that only those people go to heaven. The rest of the good people stay on earth paradise.
Your kingdom come on earth as in heaven they say.
who are the 144000 and what Will happen to earth ?
Bear in mind what heaven means. Heaven means 'heights', but figuratively it means a state of mind in which one is 'heightened', some call it 'enlightened'. After all, that's who Jesus is, the light of the world. So when a person realises Jesus and understand the spirit of holiness and good-will and knows what love is and attains that peace of mind from God, they are in 'heaven'. That's where the expression comes from, 'heaven on earth'. Heaven is the spiritual state, or the state of mind.
Paradise is the new world. A world without sin and a world where everything is understood in complete totality. A place where 'human nature' as we know it, is no longer ever prevalent over the spirit of good-will. Where everyone understands themselves to the degree in which God understands them. Where all sin is rendered pointless because all is known and everything is understood. Where the curse is gone.
The 144,000 are the number of people who are utterly true to him on Earth, before the judgement. The ones who are truly 'enlightened'. That's right, the bible itself says there are only 144,000 chosen ones to go out and show God to the world, who truly understand him.
These are the ones who show everyone to the light.
I suspect they are people throughout history who have been patient, kind, sacrificing of themselves, never quick to anger, giving, forgiving, who speak the truth, who are compassionate and loving, and who do the things of God. People who truly know God and people who truly show God through themselves. People with all the love in the world to give. Wise people. People who are humble and without self-righteousness and pride and people who perfectly capture what a human being can be when they know the true God.
I don't think it's a group of people who belong to a certain title, because even within Jehovah's Witnesses there are bad seeds and good seeds and different types of belief. A good seed is a good seed no-matter which species of plant it belongs to or which bag of seed it's in.