Click-Through Rate (CTR) is the ratio of how many impressions-to-clicks a link had. For example, if your ad had 100 impressions and 10 clicks, you had a 1:10 or 10% CTR.
CTR is used for organic content such as social media posts, as well as paid display advertising, and email marketing; as it is a good indicator of how successful your keywords, visuals, and overall campaign are.
If you have a low Click-Through Rate, it is worth analysing whether your ads are in the right place, and are being shown to the right audience. In addition to what is being shown and offered to users, the ad must be captivating, and cause them to take further action by clicking on your link.
Once you have reviewed the success of your ads, and noticed your low CTR, you can better analyse areas for improvement to increase the rate of users clicking on your link.