system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How much DNA do I actually share with other humans?

I know chimps and us share 98.5% of our DNA. However, what I don't get is how much DNA I'd share with any other odd human being on the planet. Like what's the scale? How many human-human DNA differences would it take to compare to a human-chimp difference? How similar actually are people of the same ethnicity? How different actually are people of different ethnicities? What's the real difference between how much DNA I share with my mother and how much DNA I share with a random person off the street?
gpt
The question you have to ask is what do you consider to be "different"?

Your DNA is made up of chromosomes.  Those chromosomes are organized into genes.  Your genes are then made up of base pairs.  

The base pairs are the basic informational unit of DNA - much like a bit in computer memory.  Each Gene is made up thousands to millions of base pairs.

Genes are the basic functional unit of DNA - much like a file on your computer.  Each chromosome is made up of hundreds to a few thousand genes.

We're not entirely sure why chromosomes exist - they're kind of like a folder on your computer, if the folder just had a random assortment of shit in it rather than being organized in a coherent way.

If you look at your DNA on a chromosome level every person has the exact same chromosomes (except for people with serious genetic diseases).

On a gene level, 99.9% of your genes are identical to everyone else.  The .1% of your genes that are different mostly control your visible physical attributes - like skin color.  Even among that .1%, you're basically going to have the exact same genes are as everyone else from your race.  So if you're ethnically Norwegian, chances are there is very little genetic variation between you and any other ethnically Norwegian person.

The base pair level is where you see the most variation, but even this is minor.  So lets take our two Norwegian people.  It may be that if we look at a particular 120,000 base pair long gene that both possess that there is one base pair in which there is a minor difference.  Again to use the computer example - in a 120,000 bit long piece of code, you have one spot where one person has a "1" while the other has a "0".  Other than that one spot, the other 119,999 base pairs in the gene are identical. 

And if you were to look at the entire genome of those two Norwegians you might find one or two genes that are different.  And of the genes that are the "same", there will be a hundred individual base pairs in those genes that are different - out of a total of around three billion base pairs.

The further ethnically you are from someone the more variation there will be.  So if you take a Norwegian and an Australian Aboriginal, it may be that there are 200ish genes that are different.  And of the genes that are the same, you may have tens of thousands of base pair differences.

But even this doesn't really give us a good idea of how different things are - because chances are that those 200 different genes are doing the same thing, just with slightly different proteins. 

And when you look at the genes that are the same but have minor variations in their base pairs you're looking at meaningless differences.  Maybe the Norwegian has the amino acid Isoleucine in the 453th position of a 900 amino acid long protein, while the Aboriginal has Leucine in that position instead.  Does that actually change anything about the protein?  Probably not.

The short of it is that the vast majority of your DNA is identical, with an almost insignificant handful of minor differences.  Its just that your body is an incredibly complicated system and so even a tiny handful of minor differences can lead to huge variation in terms of how people look.