Maintenance Categories

I am noticing when I review different aircraft the topic "Maintenance Category". Can somebody explain what this means?

Is it a cost situation? Is every aircraft (or aircraft family) have a different category? Is it better to have fewer categories, or is it inconsequential?

Thanks.

yes. it’s a cost situation, you can have up to 3 categories ‘for free’, every category more you pay 15% extra , but not only for this category, for your whole fleet

and yes, there a maintaince families e.g 737 is one, A330/A340 is one, you can see the maintaince category on the aircrafts info sheet