The lower your CPA in relation to your LTV, the higher your profit will be. Cost Per Acquisition is a KPI that measures the success of various paid marketing channels such as PPC (pay per click), affiliate, display, social media, and content marketing.
Your average target CPA, is the traffic-weighted average CPA that your bid strategy optimized for. It includes the average of your device bid adjustments, ad group target CPAs, and any changes you've made to your target CPA over time.