I think you mean the mechanic asked you if you had an interference motor. Motors are either interference or non-interference. Your engine is an interference motor, which means the pistons chase the valves, meaning that if the timing belt breaks, it is possible for the pistons to hit the valves when the timing of the two is thrown off by the broken timing belt. It's not guaranteed to happen, but it is possible, it's likely actually. I got lucky in the past, my timing belt broke, but the pistons didn't hit any valves. If your pistons hit any valves, you could be in for a huge repair bill.