“Clicks” is the number of clicks from a sent email altogether.

“Unique clicks” is the number of recipients who have clicked. (How many different recipients clicked on the e-mail?)

If Person A is clicking 5 times on a link, there are 5 clicks counted, but only 1 unique click.

The click-through rate (CTR) measures the ratio of clicks relative to the number of opens. CTR = clicks / opens. The unique CTR is calculated in a similar way: clickers / opens. The CTR indicates how relevant the content is for the openers.