Pithing Needle affects cards regardless of what zone they're in. This includes cards in hand, cards in the graveyard, and exiled cards. For example, a player can't cycle Eternal Dragon or return an Eternal Dragon from their graveyard to hand if Pithing Needle naming Eternal Dragon is on the battlefield.

You can name any card, even if that card doesn't normally have an activated ability. You can't name a token unless that token has the same name as a card.

If you name a card that has both a mana ability and another activated ability, the mana ability can be activated but the other ability can't be activated.

Once Pithing Needle has left the battlefield, activated abilities of sources with the chosen name can be activated again.

Activated abilities include a colon and are written in the form "[cost]: [effect]." Triggered abilities and static abilities of the named card work normally.