Annoying noise

I’ve got a 02 Nissan Frontier. Whenever I put it in reverse, it makes a loud squealing noise that continues until I’ve put it drive and have driven forward for a couple of feet. Also, sometimes when I am driving it starts making faint constant high pitched squeak. What is it and can I fix it myself?

The first hope would be worn brake pads.

sounds like worn brake pads and the device used to alert the owner, but contacting the rotor and making such a noise before damage to the rotor or total brake loss occurs…check the pads, and sometimes you may find the inner pad shot and the outer ok, so look at both, sometimes a caliper doesnt’ float correctly and can do this.