Am I getting that money again or will my balance be zero on the loan when i finish paying off my loan? Im paying back 10K I borrowed once Im done will I have 10K in my 401k?
A 401(k) loan is taken out against the money you've already put into it. When you "pay it back", you're paying it back to your own 401(k) account, with interest, so the money is yours. So yes, when you finish paying it back, you'll have the 10K back in your 401(k) account, as it was before, plus a little more on the interest.

The downside, of course, is that if the money had stayed in the account, you'd probably have earned a lot more on the long-term accumulation than on the short term "interest" that you're paying yourself.

And remember if you lose your job before your loan is completely paid off, then you're responsible for paying back the entirety of the loan balance within 60 days. If you don't do that, then whatever balance remains on the loan at the end of that time will be treated as a withdrawal and subject to appropriate taxation and penalties…and once that happens, there's no way you can "put the money back".
You're paying back that money into your own account. You borrowed it from yourself.
You get the money. It goes back into your account.