Each player’s hand is hidden information, and should not be shared with another player unless a game effect instructs a player to do so. When a card effect asks a player to show something, all players may see the revealed information.
Each player’s discard pile is open information. Players can ask to see their opponent’s discard pile at any time. Both sides of any Champion cards are also open information, and a player can ask to see either side of a Champion card at any time. When a card effect asks a player to look at something, only that player may see the revealed information.