Confused on skill checks

So on the recent 1 shot I joined

Narrator made me do an ability score check instead of non‐combat check

I was confused on this and didnt ask at the why since I wanted the game to keep moving.

So yeah, what would be the caze where you will make players do a ability score check instead of a non-combat check?

And does that mean when you do a plain ability score check you only just add the ability listed to the roll?

But yeah, when do you decide if you wanna make them roll for non-combat or just basic ability score check?

Thanks.