My battery indicator is yellow. Just started today…what does that mean?

That indicates that you have enabled the Low Power Mode option.

Use Low Power Mode to save battery life on your iPhone or iPad - Apple Support

Bubbyandsissy wrote:

Thank you! No clue why I turned that on but I have corrected.

It will turn on by itself if the state of charge goes below 20%, and will turn off when it is charged to 80% or higher.

You are quite welcome.