Why don't you talk about the relativity of simutaneity?
Why so many of us don't understand Special Relativity? Because it is too complicated.
So the whole idea of this paper is to present Special Relativity in its simplest form. If you want to explain Special Relativity to somebody, section 2 is all you need.
In his book "Relativity: The Special and General Theory", Einstein talked about this topic in length.
But to me, instead of lighting thing up, it makes Special Relativity more difficult to understand.
If you are really interested in this topic, I can share the following two points with you.
Firstly, the discussion of Simutaneity involves two different times. The first "time" is when the event occurred, while the second "time" is when we perceived the event.
Secondly, contrarily to what Einstein suggested, in order to know that two events ocurred simutaneously, it is not necessary for us to perceive the two events at exactly the same moment.
Probably you still remember this from your physics teacher in high school: By the time interval between seeing the lightning and hearing the thunder, you can judge how far away this lighting and thunder is.
In our falling apple example, it is true that the two observers recorded different times when they saw the apple touching the ground.
But after considering the factors of distance and the speed of light, the two observers do get the same conclusion about the exact time when the apple touched the ground.