The prepayment options he was referring to are options to pre-pay portions of your mortgage (often up to 20% of the original balance per year) in lump sums, penalty free during the term. So, if you ever get a large inflow of cash, and don't want to invest it, you can put it towards your mortgage. The benefit of doing this is that your mortgage balance is instantly reduced, meaning you'll pay less interest long term. Typically you can increase your mortgage payment by 20% as an alternative to lump sum payments.
Not sure if that was clear to you.
Concierge Mortgage Group