Are brake pads supposed to be able to move in the caliper?

My brakes are intermittently squealing after being replaced 8 months ago. The squeal just comes and goes as it pleases (front brakes), and one day I had the tire off and inspected them. I was able to wiggle an inner brake pad front to back by a little bit, and was wondering if this is normal and if it could be causing the sound. If it is not normal, would appling anti squeal compound to the back of the pad help? Thanks