CPC means cost per click. You pay only when someone clicks your ad. This model is best for driving actions like website visits or sales. Use CPC when your goal is engagement. CPM means cost per mille. You pay for every 1,000 impressions. This model works well for brand awareness campaigns. Choose CPM if you want to maximize visibility. Test both options to see which performs better for your audience. Adjust your strategy based on results to optimize your ad spend effectively. Monitoring performance is key to successful advertising.