A deductible is the amount you need to pay when you make an insurance claim. The basic deductible with MPI is $500. When you register your car (or motorcycle, off-road vehicle, or camper for that matter), you have the opportunity to select a lower one.
Extension deductibles are usually $300, $200, or $100, but can vary based on what you’re insuring. When you choose a lower deductible, your premium (or the amount you pay for insurance) will go up, but some claims will have the deductible waived. Basically, you pay a bit more now, which could save you some cash later.
Check out this handy deductible fact sheet to see what claims have a waived deductible. In the end, what deductible you should pick is up to you.