CTR means "Click Through Rate", which is how many people go to your website and then click through on an advert. 100% would mean EVERYBODY who went to your website clicked an advert. However, there is another side to it. From the advertiser's point of view, they are paying for each click, so they will be watching another figure. They will be watching to see how many people clicking an advert on your website is buying their product. You might have 100% CTR from your site, but if that leads to 0 sales then your rate per click might change to be less than somebody else's site where they get a 10% CTR, but 10% of their traffic converts into a sale. It's not just about the clicks.
he asked what the best CTR value is and i told him. of course,if ever visitor click on an ad, red flags would be shooting left and right.