Well all of it. At any given time, when you look at the night heavens you are looking at objects that are different distances away from you.
We must remember though- all the light is getting to you at the same time.
Think about this. Let's say you live in St Louis. Now, you have a friend in every different major city in America. New York, LA, Atlanta etc. They all agree to get in their car and drive to your house. They will all leave at the same time. They will all drive at a constant speed of 40 MPH. They will all tell you what was playing on the television when they left.
They all leave at the same time. And when they eventually get to your house, they will all tell the same story about what was on the network news and so forth. But they will all get there at radically different times. For instance, the guy coming from Kansas City would tell you the news a long time before the guy from Anchorage. But they would all have the same story about the news because they all left at the same time.
Now, let's look at the experiment a different way. Again, your friends are going to drive to your house and tell you what was on the news. But this time, they are going to leave at different times- depending on their distance from you- in order that they might all arrive at the same time (picture Christmas Day- everybody wants to get there at 12 noon).
In other words. Your friends in Anchorage and LA will leave a lot sooner than your friends in Kansas City and Chicago in order that they arrive at the same time.
This time, when they all arrive, they will have different stories about what was on the news because they would have left at different times. For instance, the guy leaving from Anchorage might have news from two or three days earlier than the guy leaving from Atlanta. The only constant factor will be that you are receiving news that is all in the past. Some of the news will be older than other news but it will all already have happened although you might only be hearing it for the first time.
That's what you're facing when you look at the heavens. The light that gets here from Proxima Centauri (our closest star) gets here at the same time (from your perspective) as the light from the furthest galaxy. But they left at different times to get here at that instant. The light from Proxima Centauri is showing you what happened only 4 years ago. But other light that you can see at any given time when you look at the stars is showing you what happened thousands or millions or billions of years ago (depending upon how far away it is).
Just like those friends who left at different times in order to get to your house at the same instant and tell you what the news was at that moment, when we look at the heavens, we are viewing the 'news' that was current when that light left that object. And that news is different for each one because the distances we're dealing with are vast beyond imagination.
So, any particular part of the sky that you look at is revealing the news from different parts of the past because the objects you view in the sky are at radically differing distances.
I don't know if that's the simple terms you're looking for, but that's as simple as I know how to put. I hope that helps.