I saw this question posted on Reddit and thought it was an interesting question:
If someone from the 50s suddenly appeared today, what would be the most difficult thing to explain to him or her about life today?
One interesting answer was "I possess a device, in my pocket, that is capable of accessing the entirety of information known to man. I use it to look at pictures of cats and get into arguments with strangers."
There have been so many changes though it is hard to pick just one when you ponder the question.