Just starting D&D, with my kids, playing the Lost Mine of Phandelver from the Starter Set.
For a spell attack — let's say on a goblin — it usually says "on a hit" then [xyz] happens to the goblin. But how do I know if the spell has hit the goblin?
OK, first I roll the d20, plus appropriate modifiers for my wizard. But then what am I comparing the resulting number to? Is it to the goblin's armour class? Or to something else?