An ability is a spell if it says it counts as a spell, or if it refers to a specific spell in the book.
For example, the drow Magic Drow the skill says:
Meet the dance lights joke. When you reach the 3rd level, you can launch the fairy fire spell once a day …
That affects both points: those are spells specific to the book that is referenced by name, and the description uses the words & # 39; cantrip & # 39; and & # 39; spell & # 39; just to make it very clear that they really are those things. So you can not, for example, use your race fairy fire If you already used an extra action to throw. curative word this turn
But the firbolg Hidden step he does not do any of that, so it's not a spell or a cantrip, and it does not restrict your ability to cast other spells during the same turn.