I am using google webmaster tools to my website. But I don't exactly what is meant by impressions and clicks? Any idea? And which one is important?
Impression = is when the user sees your link but doesn't not click it, so it doesn't enter in your website. Click = is when a user clicks a link that is triggered from a keyword, so it visits your website.
Clicks are obvious and Impressions are simply how many times a page has been loaded with your ad on - i.e. viewed
Another important measurement is the Clickthrough Rate (CTR), where you divide the # of clicks by the # of impressions. The higher the CTR the better!