What is a specific point?

Hello,
The preposition "at" is a little confusing for me. They say "use it," when you are referring to a specific point or time: at the door, at the bus stop or at the corner etc. But, as a Turkish speaker what I understand from "point" is like a period, a dot, a very specific spot and, it doesn't quite make sense in every situation. For example; at the corner is okay, because there are two lines intersecting. On the other hand, being at the door cannot be explained with the same logic; there is nothing intersecting, a dot on the floor you need to stand on etc.

I have many of them memorized, but when I come across new words, places, objects ( The possibilities are unfortunately endless ) during a conversation, I get dilemmas. At the crossroad, for example, I'd say "on," since you're literally on the road and the parallel lines... In a nutshell, if I can get what you, as a native speaker, understand from a specific point or time, I think I can sort out this problem I've been having... Thanks a million in advance!