Cookie period is the time span of the cookie that will remain in the user’s browser once the user clicks your tracking link.
In simpler words, cookie period determines the ‘transaction attribution window’ for a campaign based on Link Attribution. If the cookie period for a campaign is 20 days then it means that any Transaction/s made within 20 days of clicking on the tracking link, will be attributed to your publisher account by the advertiser.
For example: On 10th August customer clicks on the tracking link, untill 30th August if the same customer makes any transaction/s through the same browser without clicking the link again, the transaction will still be attributed to your affiliate account based upon the cookie stored in customer browser upon the time of the click.