Swagbucks is primarily a site which promises to pay users for completing surveys.
Analysis & user reviews here:
https://www.surveyssay.com/swagbucks-review/
and here:
https://www.surveypolice.com/swagbucks
More reviews here:
https://www.sitejabber.com/reviews/swagbucks.com
The SwagBucks button, to which your link refers, allows SwagBucks to track your browsing activity (although Google does that too, especially if you're logged into your Google account, and many other sites - including AB - use tracking cookies), so some users prefer to use a different browser for SwagBucks activity to the one they use for general use:
https://www.reddit.com/r/SwagBucks/comments/7drb4y/are_there_any_negatives_to_installing_the/
The 'deals' that are found via the SwagBucks button are likely to be exactly the same ones which you can learn about (without being tracked around the internet) by using sites such as VoucherCodes:
https://www.vouchercodes.co.uk