CTR gives you a good idea if people are clicking your Ad relative to your competitors. High CTR means of the Ads presented to viewers they clicked on your Ad at a high ratio. Low CTR probably means your competitors got more clicks relative to the amount times they showed up. But, its important to make sure the Ad is optimized relative to the keywords on both the Ad and the Landing Page. Main thing is pay attention to Quality Score since Google wants to show the most relevant Ads for the searched keyword terms.
How Quality Score Impacts Ad Position
Quality Score is how Google grades the relevancy of keywords and ads in your AdWords account. It’s reported on a scale of 1-10, from awful to amazing.
Why does Google care about ad quality? It’s obviously in no one’s best interests to show irrelevant ads that don’t appeal to users in the SERPs and throughout their network. Google only gets paid if people click on your ads, so they favor ads that people are likely to click. It’s that simple..
See links below for full article by Word Stream and also Google Adword Support: