Not silly at all. It's rcs which stands for rich communication service which is basically android version of imessage. So if the bubble you send is blue it means you can share files with people and see if they have read the message or see if they are typing
This one will probably sound more silly than the other one, does it mean I can send videos/pictures without it costing me extra? but thank you as it makes sense to me now.
Yes you can as long as the other person who's receiving the image/video is also using RCS otherwise it'll default to MMS and it'll be charged as your networks MMS rate