This is an old method of seeing if an email has been opened / read.
A picture 1 x 1 pixel is linked in the email with a specific name eg 'Paull.jpg'. when the email is opened the picture is requested from the senders server, so if the sender monitors the requests then they can see that Paul L opened the email. Its a very crude way of tracking and easily overcome by setting ' do not download pictures' in your email client.
@ Frances, the owners of this site do not need to 'attempt to place a tracking pixel from facebook' on this site as there is a facebook icon, bottom right of the page, that, unless 3rd party cookies are disabled in your browser links directly back to facebook, same for twitter and pintrest.
Third party cookies are the primary way you are tracked around the internet and 3rd party adverts are one of the biggest infection vectors for malware. Apple has never allowed 3rd party cookies on there products, Google has indicated that they will also ban 3rd party cookies in the future.
There are other ways to track people such as Super Cookies and also Browser Fingerprinting but these can also be managed.
Clicking on link in emails is a serious problem and should be discouraged as should opening attachments.
Paul
Edited By Paul L on 17/02/2021 11:56:16