Please help I'm really trying to understand how deatils in a story or excerpt develops a character in order for me to write this essay
Details are what you use to create the character in your mind. Let's just say I told you my car is red. Well, no big deal, right?
Now, let's just say that my car is ...
a candy apple red Bughatti with kickin' rims and a killer stereo. It has soft, black leather and the darkest window tint I could get, which I don't think should be legal. I broke 200 mph in it the other day on the racetrack and don't think I will ever find a car I love more. The stereo has so much power and I just love the bluetooth feature. Man, I just love my car!
Now ... which car can you envision? My first description or my second.
That is how you develop an object.
You can easily do the same for a character by describing looks, sound, smell, feelings, etc.
Just describe the character. That is what the details are for.
Hope this helps.