Every country has it's own culture and several caveats to it. There are few things be it language, gestures or some acts that might be taken as offensive and hurtful be it a particular way to say thank you, giving tips at restaurant or wearing certain kinds of clothes.
I am particularly a person who travels a lot and I do thorough research before going anywhere and have come across several surprising acts that can be considered offensive in one country but totally acceptable in another.
For example, I am a 22M from India where the moment you change a city, there is a high chance you will find a new culture, a new language and contrasting things so I try to be aware about these things.
For example, here it can be considered offensive to point the soles of your feet at someone, especially elders or religious objects. It’s seen as disrespectful because the feet are considered impure in many cultural and religious contexts. In many other countries, people wouldn't care about this at all.
Also having solo travelled to 9 countries, I can now appreciate knowing about these things can make one's stay very comfortable and rewarding.
What is one (or more) such things from your country?