PAL is an acronym for Possession and Acquisition License. A Non-Restricted PAL will allow the license holder to both possess and acquire both firearms and ammunition. Since 1995, this has been the main, basic gun license in Canada. It is sometimes referred to as an NR PAL.
RPAL stands for Restricted PAL, an upgraded license class including handguns that are not otherwise prohibited, as well as short-barrel rifles and shotguns, and other firearms specified by the Criminal Code Regulations.
POL stands for Possession Only License. A POL historically allowed the license holder to possess (but not acquire more) existing firearms, and allowed the POL-holder to purchase ammunition. This license type is discontinued. Valid POL-holders as of September 2, 2015, automatically became PAL-holders that day under the new 2015 Firearms Act. If your POL expired before September 2, 2015, you may – at the RCMP’s discretion – need to recertify for your PAL in a classroom course.
FAC stands for Firearms Acquisition Certificate. This was Canada’s gun license between 1977 and 1995. They have now all expired and need to be replaced with a PAL.
Expired POL-holders must either apply for a PAL with the RCMP, or surrender their firearms to someone with a gun license (or the police), as firearm possession in that situation is technically illegal.