Einstein's theory of relativity is actually TWO theories: special and general relativity. Basically, special relativity introduces two postulates: First, the laws of physics are the same for every inertial frame of reference and second, the speed of light is constant for all observers. General relativity, introduced a decade later, expands the theory by adding gravity to the mix.

Einstein's relativity replaced the three-dimensional Newtonian model of reality with a new four-dimensional model of space-time. Time was no longer fixed, but fluid, and was now an integral part of the fabric of the universe. Einstein's relativity theories are most notable for the curious, counterintuitive predictions they offer, from time dilation to the equivalency of mass and energy to the gravitational bending of light.

The theory of relativity connects time and space. The Faster you go the slower time goes. Here's an example. Imagine you are driving in a car at 60 mph going northeast. This means that you are going 30 mph in an easterly direction and 30 mph in a northerly direction. As you slowly veer your car to the left (north) you begin devoting more of your speed to north rather than east even though you are still going 60 mph. You are now going 45 mph in a northerly direction and 15 mph in an easterly direction.

Now imagine if you will that North represents Space and East represents Time. If you are moving faster in space it makes you move slower through time. However these effects are only noticeable if you are going at sub light speeds.

Just take an example that you are with someone you love the most and condition is you will have 2-3 hours to spend with her. You have al the arrangments to make a very special evening and dinner as well. So time goes like a super express train. You would always want to stop time a bit but can not.

But lets compare your time with someone in a boring lecture. He would feel like years to sit for an hour in class. So time is relative with respect to people and place as per Einstein. He quoted the famous theory to explain that time moves slower if you travels at lightening speed as compared to normal people.

The theory of relativity is a physics theory developed by Einstien. This theory explains that all objects appear to be in motion or at rest relative to the point of observation. In simple terms, what appears to be in motion to one observer, may not appear to be in motion to some other observer. Similarly, what appears to be at rest to one observer may not appear to be at rest with respect to another observer. Thus, the terms 'motion' and 'rest' are relative to the observer. It cannot be said that the state of motion of an object is same for all observers in the world.

...I'm going to go with 'no'.

I can understand the calculations related to the consequences of realtivity like changes to mass, length, and time as speeds approach the speed of light, and the equivalence of matter and energy.

How it all relates to inertial reference frames was never something I could grasp. (I had a physics professor once who said there may be five people in history who really understood relativity and not just its consequences)

Theory of relativity is simple.

Everything is either mass or energy. One can be converted into the other through some process or the other. But neither can be produced or destroyed.

The conversion of one to other is through the famopus formula E=mc2.

c is the speed of light. Beyond this speed, nothing can travel. This is the limit to our lives. Above this speed, mass converts into energy.