so....
Beware emails that tell you about this sort of thing. Sounds highly likely to not be legitimate.
Tracking pixels are tiny (often 1 pixel x 1 pixel) images that websites use to gather data about your behaviour, user info etc.
More for selling you shit you don't want in a 'targeted' way than anything more sinister.
While I don't like that stuff, I'm highly suspicious of why it would be mentioned in an email.
Whatever you do, don't click any links in that email, but please do tell us a bit more about it.
Sounds very suspicious to me.