A long time ago, I read a thought experiment from the British philosopher John Locke, and it was what inspired me to go on to study philosophy. It's a question and a thought that I suspect many people have as well. It goes like this: imagine that there are two perfectly healthy people with perfectly functioning sense organs, and they are on a walk, and one turns to the other and says, "Wow, look at that beautiful blue sky!" And the other one nods along and agrees.
Now, the question that John Locke asks is: how do you know that when one person sees blue, the other person doesn't actually see green? They both call the sky blue because that's what their upbringing has taught them. But the content of their colour is different, and there is no way of knowing.
You can say, "Let's point to all of the things in this room that are blue," and the other person will of course get that right, but that is because they associate the word blue with all of the same things as you, even though they actually see green inside their heads. They have what philosophers call different "qualia."
John Locke's thought experiment is not only fun, but it raises the problem of other minds, because we are all trapped inside our tiny cranial towers, and we can never check what life is like for somebody else. We have only a sample size of one, and other than telling you, I can never know what it's like to experience life as you experience life.