2021-04-16
Activated abilities contain a colon and appear in the form "[Cost]: [Effect]." Some keywords (such as equip) are activated abilities and will have colons in their reminder texts. Loyalty abilities of planeswalkers are also activated abilities.
2021-04-16
An activated ability that costs mana to activate is not a "mana ability" unless it could also produce mana and has no targets.
2021-04-16
Casting Revel in Silence in response to a spell or ability won't affect that spell or ability. That is, it's not countermagic.