Yeah so basically :
- ASK HN : To Ask HN something. Make sure it's a legitimate question and re-read it to yourself to make sure it makes sense. It's not for asking questions like "How to do a binary search?", that belongs elsewhere.
- SHOW HN : To show HN something that you built ( or someone else did ) and receive feedback on it. Don't spam the same thing over and over, your account might get marked as spam, I learnt it the hard way.
- LAUNCH HN : It's for YC startups when they launch.
Apart from this, you should feel free to post anything new and interesting that you find on the internet. Primarily tech-related but not necessarily. Anything that helps quench curiosity and isn't spammy works.