When the FDA accepts a drug application it assigns a review track. Standard review targets a decision in ~10 months; priority review targets ~6 months, for drugs that, if approved, would be a significant improvement in safety or effectiveness.
Standard review~10 months
Priority review~6 months
What it signals — and doesn't
Priority review reflects the potential importance of the drug, not a higher approval probability. Plenty of priority-review drugs get CRLs. It mainly compresses the timeline — useful for catalyst timing. Related: what is a PDUFA date.