Gravity or gravitational attraction is the force of attraction between two bodies with mass including stars , planets , galaxies and even light and sub-atomic particles.
It is directly proportional to the product of the masses of the bodies and inversely proportional to the square of distance between their centre of mass (in case of spheres, it's the radius).
While thinking about space, an inch or some feet are thought to be nothing. But science knows what that single inch can do. Just a trifle change in the mass of proton (consider 'trifle' for atom), can change the whole structure and stability of nucleus. Its force of attraction with electron, mutual understanding with neutron, and who knows what will change. Then the structure of the atom will collapse which in turn will result in the collapse of matter. With this, the whole universe will collapse because anything that has mass and occupies space is matter.
Imagine the destruction caused by something very small for a thing which was once considered to be the smallest, atom.
So, Gravity is the known God.
In simple words, just to boost your imagination, GRAVITY IS THE FORCE OF ATTRACTION BETWEEN TWO BODIES THAT KEEPS THEM TOGETHER OR BOUND IN A WAY.
Thus, everything is connected. That means we also exert force of gravitation on those huge stars. Yay! But it is another thing that those stars don't feel it. Curse their massive mass!
Everything in space is kept in its normal position due to the virtue of gravity. The spherical form of planets and stars , fixed pattern of orbits and galaxies - are all due to gravity. Also , earth and other planets are revolving around the sun in its normal orbit because of the gravitational force of attraction.
Earth attracts objects towards it with its gravitational force. Hence we are able to walk on Earth, our atmosphere and hydrosphere don't escape into the space.
Hence, earth's gravitational force is responsible for keeping everything in order and its normal position.
If Earth would not have gravitational force, then air will escape into space creating a vacuum and it will be like another barren planet.
It will lose its sky, all the spheres, atmosphere, hydrosphere and that will turn the lithosphere into ruins and eventually, biosphere will be vanished.
Also, the moon will escape into the vast universe until it finds its new planet to revolve around or maybe, it could get crashed with some other planet.
Gravitational force acts over an infinite range and mass.
On the macroscopic scale, it acts as a force which binds them together or bring them close.
Here , the Newton's law of universal gravitation is applied.
Where, G is the gravitational constant
m1 and m2 are the mass of two bodies
r is the distance between them, from the points of their radius.
We think that the Earth without gravity will be like an amusement park with free rides and no tickets. We will be flying in space. Our hair will flow and we will feel no weight. Amazing? Not really. Because this is not some children fairytale. Without air, we can't breathe. We can't even survive in space! Our Earth will be ruined. The Sun will attract Earth towards itself. We will be burnt as ashes.
Believe it or not, Gravity is the most powerful and mysterious natural force which gifts so much when cared for and destroys everything when played with.