PRM means promotional. This is a review of your credit by someone who is trying to decide whether or not to make you an offer of credit. For example, a bank looking for good people to send a preapproved credit card offer to. Chances are that this is someone you have not dealt with before. AR is an annual review. It is done by one of your creditors to make sure you are still paying your other creditors. They want reassurance they did the right thing in extending you credit. You should recognize their names as your current creditors. My understanding is that both of these are soft inquiries.
PRM: promotional inquiries. AM or AR: periodic review of your credit history by one of your creditors. PRM, AM and AR inquiries are soft --they don't show on credit files that lenders receive, only on copies provided to you and remain on your file for 12 months.