Before this man came along we lived in a comfortable world where space and time were considered independent and absolute entities. Fixed dimensions we had no trouble understanding and working with in our minds. Albert Einstein changed all that forever. For those (like me) who bother to become aware of it life will never be the same again.

Space and time as we understand them now are closely interrelated, and combined into one single entity : spacetime, which is not "absolute" (fixed) but flexible and can buckle, stretch, contract, bend under the influence of gravity or energy. As Einstein put it :

Einstein's publication of his Theory of General Relativity in 1916 put the sciences of physics and cosmology on an entirely new path of discoveries, uncovering amazing aspects of reality, which are hard or even impossible to comprehend by the limited human mind.

Brian Greene in his book Fabric of the Cosmos (I have referred to previously) has documented much of this, explaining it in easy to understand common layman's language. Here follows his visualisation of time.

Time is not like a dynamic flowing river, rather it is like a frozen block of ice. Consider an elongated block of ice, cut in parallel slices like a loaf of bread. Each slice represents a "NOW" moment in your life. And of course as your notion of time progresses you proceed from one "NOW" slice to the next, and the next, and so on.

On the Diagram below your past is shown in purple. The thin dark purple lines are "NOW" slices you lived through moments ago. The thick purple line is you NOW point right now, while the pink future is ahead of you.
No matter where your two friends John and Pete are, as long as you all three are stationary (or sit with you in a car or plane traveling together at the same speed and in the same direction) your three NOW slices coincide.
But as soon as you each move at different speeds in different directions the picture changes dramatically.

John, who was with you talking to you a minute ago, steps into his car and drives away from you. As an immediate result his NOW time slices are rotated at a small angle to yours, cutting through your past.
Pete, who lives 50 km away at the other end of town (who just phoned to say he will take you to dinner) has also jumped into his car and is now traveling towards you. Pete's NOW time slices have also rotated slightly with respect to your's and are now cutting through your future.

It is important to realise that this is not just theory. It has been proven with high precision clocks in airplanes flying around the world. The larger the speed difference between the two people the larger will be the angle between their two sets of NOW slices. And the farther away the two people are from each other the deeper they cut into each others past or future.

Here on earth the differences are minute and not noticeable in daily life. Modern planes however do take the above into account with respect to their flight navigation.
But let us take a hypothetical living creature - we will call him Max - who lives far away on a planet in a galaxy 10 billion light years away. You and Max sit quitely in your perspective living rooms perhaps watching the evening news on TV, and although far far apart you are both on the same NOW time slice.
Suddenly Max gets up and walks outside to do his daily exercise, jogging at around 10 km per hour. If he is running away from you his NOW slice will cut 100 years into your past, well before you were born. If on the other hand he decides to jog towards you his NOW will be 100 years ahead of you into your future, when you will be dead for sure.

Do the same imaginary exercise while Max is sitting in an airplane and the NOW time slice difference has increased to a wacking 10,000 years !!