Symbols on the - Guide - what do they mean and what are they for?

[thisisnuts2017]

For instance when browsing the guide using subscribed channels.   I see for example on cartoon network HD (757) and underneath it, I see a little symbol of a movie reel and a blue button.  (I see the symbol for only some channels not all).

So when I look up the guide legend, for that symbol it says - browse on demand.

So why is this symbol there on only select channels? I mean, am I missing something here?  Is there some type of option that I am unaware of?  We have the "on demand" button for our controller that we use to view - on demand. But for the example I've given - in the on demand section, there is no cartoon network HD. 

Needless to say this is confusing on the menu.

Does anyone know why it is there?

Thanks in advance

[tns2]

Browse on demand.  I.e. that channel has some a On-demand version of at least some of its programs.  You can select left

then OK to see if you can find the program you are interested in.