Here are the key points in 3 sentences:
CTR measures the percentage of people who click on ads and can be increased by optimizing ad placement, size, and blending ads with site content. CPC is the amount earned per click and depends on ad relevance, traffic quality, and competition. eCPM is a performance metric calculated by dividing total earnings by thousands of impressions and can be improved by increasing clicks or paying ads through high quality content and optimizing ad placement.