The Oxford English Dictionary defines gatekeeping as the activity of controlling, and usually limiting, general access to something.
The term gatekeeping goes back many years, when towns and villages had physical gates. Back then it was in the residents’ best interest to keep certain people out of the village.
Nowadays the term refers to keeping people from doing things they enjoy doing. Either trying to keep them from doing it, or plainly telling them they’re doing it wrong.
Gatekeeping what people may, or may not do has now become quite widespread in our world.
Some will try to gatekeep everything from suffering and pain, to how long a person should sleep, or exercise. They will try to keep others out of fandoms.
The basic premise for the last one is “I’ve liked this thing longer than you have. Therefore you are not worthy.”
I have always – apparently mistakenly – thought that if I like something, I want other people to like it also. Clearly not, according to the masses.
“We want to keep this thing for ourselves” they are saying.
“The more, the merrier” is what we should be saying.
For more examples of gatekeeping, have a look at r/gatekeeping on Reddit. You might be surprised what you may be doing wrong.