Your brake pads are worn. When they wear down a metal tab(wear indicator) rubs on the rotor to let you know it needs attention. Let it go too long and you'll need new rotors if the current ones aren't trashed already.
New pads installed properly and rotors resurfaced or replaced. Installing new pads without resurfacing or replacing rotors is worthless. The pad life will greatly be reduced.
When it's all taken apart the slides, retainers, pads, and shims need to be lube to get the most out of your brakes.
The brake caliper should move, that's how it applies pressure.
If it's not the pads, then it might just need a brake service, which should be done at least once a year.