Yes, "revealing" cards means to show it to all players.
The library is a so-called "hidden zone", meaning the cards in it are not visible to everyone.
400.2. Public zones are zones in which all players can see the cards’ faces, except for those cards that some rule or effect specifically allow to be face down. Graveyard, battlefield, stack, exile, ante, and command are public zones. Hidden zones are zones in which not all players can be expected to see the cards’ faces. Library and hand are hidden zones, even if all the cards in one such zone happen to be revealed.
It requires a special effect to look at some or all of the cards in a hidden zone. As the first sentence states, you have to reveal the top 5 cards before you choose some of them to put in your hand. You have to show all the players which cards you chose to put in your hand.
Rules for revealing a card:
701.14a To reveal a card, show that card to all players for a brief time. If an effect causes a card to be revealed, it remains revealed for as long as necessary to complete the parts of the effect that card is relevant to. If the cost to cast a spell or activate an ability includes revealing a card, the card remains revealed from the time the spell or ability is announced until the time it leaves the stack.