what is close capture?

on my tv-tunner i have something close capture....what does it to?
if i selsct "enable" i get to choose from something like channel 1 or 2 and select a file name .txt and i have something like Alert token...
i will attach a file so you can get the idea
so my question is...what is this?

Closed Caption

Simply... it's a text "speech bubble" that can be superimposed on your TV picture -- if you have a decoder :?

"Closed" because it is normally hidden
"Caption" - a short text

**broken link removed** for more info