By "party", I mean a physical social gathering of people for the purposes of having fun. It may be used in a sentence as "I am throwing a party!" or "Let's party!".
Basically what I am trying to say is the default "party".
I've never been to any, and I have no idea how people spend their time on parties, so I am curious how you did.
You're not the first one saying a person should arrive late. Why is this a thing? Is it just a cultural norm in the West? Or is it a thing everywhere?
Because arriving at a party when there's not many people around can be awkward especially if you aren't already friends with the host. So you wait for more people to arrive first.