CPM measures exposure
CPM shows the cost of 1,000 impressions. It is common in reach, awareness, display, video, and publisher reporting.
CPC measures clicks
CPC shows the average cost of one click. It is useful when traffic is the immediate campaign goal.
Use both with context
A low CPM does not guarantee clicks, and a low CPC does not guarantee conversions. Review CTR, conversion rate, revenue, and profit alongside cost metrics.