To me, inside jokes are black and white matters. You love them or you hate them. You have them or you don’t. There aren’t any in-betweens. There’s no, “Oh, well I kind of have an inside joke with my friend, but I’m not sure.” Nope. If you have to think about it, chances are you don’t have one. You and your friend will both undoubtedly know if it’s an inside joke or not.
According to Urban Dictionary, an inside joke is, “Something shared usually among close/best friends. When you can say a simple word or phrase and be sent into hysterical laughing, that word or phrase is an inside joke. To other people who are "outside", the ones who are "inside" seem preppy, stupid, and immature.” To me, this definition is pretty accurate. However, I also think that inside jokes can be extended to gestures and events. For example, if you and your best friend witnessed something that you both found extremely hilarious, every time it happens in the future, you might make eye contact and bust out laughing.
Inside jokes don’t happen randomly. They are rooted by memories of some incident that you and your best friend found memorable. They are a sign of true friendship. It means that you and your friend or whoever you are joking with have such a strong relationship that you can see something and give each other “the look” and start laughing uncontrollably. It means that you can make the most insignificant moments funny and memorable. It means you can create memories and have dorky ways to remember them by.
These silly little jokes that make sense to only a few people are great don't get me wrong, but they are still criticized. A lot of people get uncomfortable when they're around other people who are constantly making inside jokes. They may feel left out. They may feel confused. They may feel like the most mature person in the group. No matter how they are feeling, they don’t know the joke. Along those same lines, some people think inside jokes are cliquey. I am in no way promoting the elimination of inside jokes, but I do think that excessively saying jokes to only one person in the whole group can be annoying. If you absolutely can’t refrain, by all means, tell your jokes. But once your purpose is to use inside jokes to hurt others’ feelings, you’ve gone too far.
Inside jokes truly can help make the best of any situation (with a few exceptions). Maybe you had a bad performance or did terrible on a test. Yeah, it will suck at the moment, but maybe you and your friend will be able to look back on the situation and laugh about it. Eventually, that laughter can turn into a joke that you'll have with you for the rest of your life. Even if you think inside jokes are dumb or immature or even rude, don’t be afraid to have them.