Trackers

I have recently changed browser to Brave, and it gives me a list of things it blocks. Every time I use FF, it tells me that it has blocked a tracker, and FF is the only website I visit with any regularity this occurs for. I am not a computer whiz by any means and when I googled 'trackers' I only got information about torrent trackers.

@TAFKAP any idea what these trackers are?