At the end of a lease you're expected to return your vehicle to the car leasing company with no more than normal wear and tear. You'll have to pay for any damage or extra mileage over and above your contract-specified limits.
This is regulated by our industries BVRLA
You may have an option to purchase your vehicle at lease-end for usually a price between trade and retail, if you choose.
Otherwise, you can simply return the vehicle to the leasing company and walk away.
Making the best decision about what to do with your vehicle at lease-end — returning it to the leasing company, buying it, or extending your lease — requires that you look at each option carefully and evaluate.