The topic of projection. What is it?

I hear examples of it. People say if you don't like this particular quality in someone it means it's something you don't like about yourself. Do I understand that correctly?

Is that what projection is ? Do I have a basic understanding of it? I can go into more examples, but I would like some input.
I always found it the topic very interesting and complex.

Ok. Well here are my examples. You tell me me if that is projection.

I sit in starbucks, I waste time. I see a bad pattern with my life

When I see someone else sitting in starbucks who appears doing a similar thing that I do. In my mind i classify him as a loser. Or lets say it's someone I briefly spoke to and got the feeling he is wasting time like I do. So every time I see him it upsets me.

Here is a better example, you don't like a friend that is easly upset
Loses his cool. Eventhough you loss your cool easy. Is that a better example?

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Lose*

You're talking psychological, okay. I always thought it had more to do with...how do I say this where it makes sense. For example, say you accuse others for their own bad behaviour but you are guilty of doing the exact same thing but deny you do it. Like a bully who picks on others because of their own insecurities. It think it works both ways too, it doesn't always have to be negative, like say you praise another person who does something good which you've done the exact same thing yet don't acknowledge it, a positive psychological projection as opposed to a negative psychological projection. I think there are other types but I'd have to Google it. That's just something I come across regularly.

So for what you said above I'm not sure if it fits into the examples I gave, you seem to be aware of it and don't deny your own problems exist. I dunno, I'm no psychologist but interesting topic.

Yes, as I said it gets complex. You have a friend. And you know when you start accusing someone in lets say an argument of doing or being a certain way, they will try to defend themselves by saying you are just projecting! But even, so. Is there no truth to it?
If someone has a similair personality flaw as you do? Is projection? Thats where it gets confusing

The grownup equivalent of 'Takes one to know one'. Attributing your own underlying desires and thought processes to others out of subconcious guilt.
It's an (overused) method of fending off personal attacks in debates, a bit like "gaslighting".