What is time???

We never think about time. if we think we just say leave it. If anybody ask anyone about time that what is time? Some says time is money, some says time flies , some says we waste our time, some says we kill time we murder time but actually no one knows about time. we all know the property of time that it flows like an arrow and travel only in one direction from past to the future.  In scientific way time is the indefinite continued process and event  that occur in apparently irresversible succession from the past through the present to the future in short the flow of time is from past to the future and unidirectional in nature once it goes it will never come back .

As per of the theory of einstein ,black hole theory,quantum mechanics and many more theory it is concluded that time depends on the following factors like-

1) restness and the motion of an object in space
2) on the gravity
3) on distances (depends on distance between the respective object with reference to space)

So these are the major three factors in which the time depends upon.

First, it is found that the motion through space slows the passage of time that means if we are travelling with the speed 30km/hr  with respect to space time passage will be faster than the object moving at speed 60km/hr overall conclusion that if our speed increases the passage of time decreases vice versa but now the question arises if these thing is happening then what is the speed of time ???? Is it fair to use word called speed in case of time?????

Second, if i will say that gravity is itself an function of time yes ,its true its very hard to believe though . Albert einstein the great scientist said that more is the gravity strength slow will be passage of time for example as we know gravity of moon is less than earth so in moon the time will flow faster than earth it also explains about the 3rd factor that time also depends on distance the distance between earth and moon is so less as compared to the whole universe so its very difficult to observe the changes.

Let me give an another example, their are two man named sam and john imagine that sam used to live in the building on 30th floor and john used to live on that same building but at ground floor so generally we know at ground the gravity is more as compared to the distance from the ground so john's time will flow little bit slower as compared to sam and similarly the 3rd factor distance also matter though distance between seems to be neglegible compared to universe system so it didnt shows up.

It's just the history of the universe (or some interesting facts), consisting of events at different times and positions, considered as a four dimensional space. And of course it was always a four-dimensional space in a trivial sense that you needed four variables (x, y, z, t) in relativity it becomes four-dimensional , because you have a measure of distance in it, called Spacetime interval.
Our eye is compatible to only 3 d structures not to 4d. But time remain in the 4 dimension in space.

Now the question arises that is time is an illusion???

If time is an illusion, then how can you assign a mathematical variable to it? Is it normal procedure for physics to assign a physical variable to an illusion? What I mean is, for time to be slower near galaxies than in empty space, time must be real. Only real things can go slower or faster. An illusion cannot go slower or faster. A car can go slower or faster; an illusion cannot. So now even after these the question remains the same what is time?????????