According to the Merriam- Webster dictionary, culture shock is defined as "a feeling of confusion, doubt, or nervousness caused by being in a place (such as a foreign country) that is very different from what you are used to."
This can come in many different forms and originate from many different places; including language, customs, foods and general behaviors of the people who live in the country you are visiting. This feeling can range from minimal to extreme depending on previous travel experiences as well as the home culture of the individual.
Personally, I experienced intense culture shock when I traveled to China a couple of years ago. There was an obvious language and culture barrier but I also had an intense feeling of uncomfort during the majority of my trip. Being blonde and white, I stuck out immensely among the thousands of people in Beijing. Where in America, the most shocking reaction to somebody who looks different than you would be a stare or slightly rude behavior, I was nowhere close to warned about what I would experience.
Throughout my trip I was constantly touched, gaped at, taken pictures with and followed. I came to learn that this was actually not uncommon at all and other people I was traveling with experienced the same behaviors. Although I never really got used to random people running their fingers through my hair when they walked by, I tried my best to ignore it as the time went on. There are certain things that they do not tell you in travel manuals and on the internet; this was definitely one of them.
If I could offer one overarching piece of advice regarding culture shock, it would be to expect the unexpected. And if something happens that you are not used to or seems odd to you, do not react negatively to it and use it as a chance to learn! Every place has its quirks so appreciate them!