Is there a rule about ":" this? Like when should I use this?
Answer from a Native speaker
Yes, there are a few rules to use the colon ":" in writing. A colon usually leads into something following it, such as a list, or after certain phrases like "as follows" and "for example." You can also use a colon before a conclusion, as used in this video. You could use it before a quote or phrase, and you could use it before the subtitle of a book or movie. Ex: To make the pasta dish, we need: onions, tomatoes, pasta, and herbs. Ex: My friend once said: "Motivation is an illusion, just do the things you need to do." Ex: He finally told us about his past: he was once a famous musician. Ex: I can't wait to watch "Spider-Man: No Way Home." Ex: As follows, this is what the letter contained: "Dear mom and dad..."