All dialogue checks are ability checks, as are perception (or investigation/nature/arcana) checks to notice things in the world, stealth checks to avoid notice, lockpicking and trap disarming (is this still Dex-sleight of hand or is it Dex-thieves tools?). Essentially, every d20 roll that is not associated with an attack or a spell/ability/trap/death saving throw is an ability check.
I don't disagree that the types of checks, and many other D&D 5e mechanics, should be explained better in the tutorial/character creation screen.
So a skill check is the same thing as an ability check? That helps clear things up.
