To expand on the question, while there are a lot of obvious differences between now and 1950 in terms of technology, culture, etc., I wonder which changes or new things they’d grasp easily and which would be utterly perplexing.
If someone from the 1950s suddenly appeared today, what would be the most difficult thing to explain
Not sure how our would explain a smartphone. You have to know something about email and web browsing.
I fear that, if anything, they would be underwhelmed. “What? No Colonies on Mars? No flying cars? All you’ve got are small phones and typewriters with screens connected to each other? Pah!”
I guess that the thing they would find more shocking would be superficial changes, like the more casual clothing or the lack of hats.
The fact that we have a black President. There were computers in the 1950’s. Science fiction of the 1950’s and earlier foreshadowed a lot. And the Devil’s Rock & Roll explains Miley Cyrus’s twerking 60 years later.
The end of the Cold War and the dissolution of the Soviet Union.
The gender and ethnic changes in politics and sports would probably be startling considering both were largely the exclusive domain of white men back then. I think the overall increase in the standard of living too would be a surprise, how most every home has a number of televisions, comfortable furniture, food in the fridge and often multiple cars in the garage. The movement of women from homemaker to salaried employee, often in management would be a shock. But perplexing would also be why if we have all these things and have solved so much do we still have an unacceptable infant mortality rate and in places an inexplicable level of poverty and homelessness.
I don’t think cultural changes would be as stark as some claim. The roots of many of them were clear in the 1950’s. The internet, now that is something completely on another level.
For someone from that time, a half-black President now? Meh. Hot, white female celebrities openly & proudly dating black guys? That would give them a stroke! 
Reported for forum change.
The most difficult thing to explain would probably be how and why people have become so stupid.
“Lemme see if I get this straight—they let people who can barely read, write, or perform grade school arithmetic graduate from college now? And people have stopped vaccinating their children because a criminal and a Playboy bunny told them that doing so will cause a developmental disorder that resembles severe schizophrenia?”
How we have smart phones that are actually computers more powerful than any they were ever likely to run into…
…and yet still don’t have intelligent robots.
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This is more of an opinion/speculation thing than a factual question.
Moving thread from General Questions to In My Humble Opinion.
In the 1950s, Pearl Bailey nearly destroyed her career by marrying white jazz drummer Louie Bellson. People wouldn’t bat an eye at that nowadays, either. And Robert DeNiro seems to have always had a thing for black women.
That we landed a man on the moon in 1969 would be hard to explain. The cost of things would too. The Internet would be easier to explain: just describe it as an updated version of the telegraph.
That people are rich enough to have two television sets
Back then, autism was thought to be caused by bad mothers. And in the 1950s, most parents would have loved to have vaccines for common childhood diseases. Being able to prevent polio was mind-boggling enough.
Pretty much everything Bruno Bettelheim has ever said has been debunked, and Jenny McCarthy’s son does not have autism, either. He has Landau-Kleffner Syndrome, a disorder with autism-like symptoms.
And while we’re on the subject, disabled people are now mainstreamed into society and not “put away”. Certainly there are situations where this has to be done 
, but it’s not a disgrace to have a disabled family member. It just is. Most parents nowadays also know that if a child has a difference or challenge of some kind, it cannot be punished out of them.
Ben Affleck as Batman.
Technically, society is getting smarter. The flynn effect stated that IQ points have been rising to 114 ever since 1914. A person from the 1950s would score around 70 by today’s standards.
Medical advances would be mind-boggling to a time traveler as well. Birth control in a PILL? Blood pressure medicines that aren’t worse than the disorder they’re being used to treat? People are having their cancer treated with MEDICINE, especially childhood leukemia, which is no longer an automatic death sentence??? Organ transplants and joint replacements? Dialysis available to anyone who needs it? Premature babies born beyond a certain time in pregnancy seldom die, and often go on to lead completely normal lives? Open heart surgery?
None of this happened in the 1950s, except for dialysis and some chemotherapy being available on an experimental basis.
Gay marriage being legal, gay senators, gay congressmen, gay governors, gays in the military, body piercings, tattoo’s, Mohawk hair cuts, purple hair, legal marijuana in Washington State and Colorado and why the San Diego Chargers can’t seem to win enough games to get to the playoffs this year even though they have one of the best teams in the NFL.
As a few people above have noted, much of the technological and social change would be an extrapolation of trends already occurring in the '50s. I think they could comprehend that a black president could be elected, although they might not think much of the idea.
Gay rights, on the other hand, from tolerance or acceptance all the way up to marriage equality, would flip them right out.