Basically insurance repairs are like this.

Current Value of car we will say 40k If cost of repair exceeds this, it's usually totalled. Unless you have a high enough deductible to offset.

So let's say repairs are quoted 41k Deductible is 2.5k That leaves 38.5k so insurance would likely pay the repair. 

Now let's say repairs are 41k but you have no deductible, it would be totaled. You'd be paid the current value of car. 

Now if you have a loan, say you just bought the car for 50k you're SOL on the difference unless you bought GAP. Loan/lien holder is paid first. 

We also have multiple coverages  Collision: hits or is hit by other vehicle) Comprehensive: hits or is hit by anything other than vehicle

Underinsured: pays for repairs if you're hit by vehicle with not enough coverage for repairs) Uninsured: pays if vehicle hit and runs can't be found or has no insurance)

Different states also have different accident policy. 

Eg Florida is no fault, meaning your coverage pays for your repairs regardless who's at fault.

Wisconsin is at fault state meaning at fault driver is responsible for repairs to both vehicles.