What does the Tracked feature mean in the game collection?

[AlphaCielago]

Now don't laugh but, I have been wondering for some months now what the Tracked feature means in the game collection. Every time I go and add some game to my collection, like recently, that button drives me mad. What does it mean?

 I have had several teories through the months that it means that the game has been mine or played at some point in my life, but is not longer with me.

I may not know what it means because of my English knowledge, but I can't figure out what it is supposed to mean in the context it's in.

 

If this thread is in the wrong forum, then give me a notice or something.