could someone tell me what is Ardor as a coin?

i googled and read alot about it but still have questions.

as far as i understand Ardor is a platform (parent chain) and Ardor as coin has less features. On the other hand ignis is a child chain in Ardor Platform with lots of features?

so what is the purpose of having Ardor as a coin in the Ardor Platform? Does Ardor miners earn fees or something for every transaction being made in child chains?

thanks