Here and there. Imagine you're holding a picture of yourself, maybe a group photo from school. You find yourself in the picture, point and say "there I am". Now imagine you're in a room full of people and someone shouts "Alisa, where are you?!" you'd reply "Here I am" or "I'm here". Hope this helps, Send me a message if you'd like more help

Location-wise, think of a room with 4 corners. There is corner A, B, C, D and you're standing in corner A. Thus, "Here I am, in corner A!", if another person is also in the room with you, in for example corner B, they are, to you, "over there, in corner B". But you can also speak about yourself in a more narrative voice. If you're telling a story about something you did, perhaps you are telling about this strange room to a friend. You went to bed the other night but somehow you woke up in this strange room with for courners so you tell your friend: "I don't know how I ended up in the room, but there I am (or was) in this strange room with four corners!" This is at least what comes to mind when I see your question :)

They're not the same. When I think of a person saying this, in succession, it probably relates to magic or a fantasy show/movie. As an example, the character would say "here I am" as they're pointing out to another character. Then follow up with "there I am", as in, they created an image/illusion/copy of themselves.

"Here I am" – when you want somebody to find you "There I am" – when you point to the image of yourself on a photo