That entirely depends on the position and whose move it is.
If it is your move and you do not have any other pieces that can move, then it is a stalemate and the game is drawn. If you do have other pieces that can move, the game simply keeps going.
If it is your opponent's move and he checks you and you cannot block the check, it is checkmate and your opponent wins. If he does not check your king, then the game just goes on.
No, a king cannot check another king in chess.
No, you cannot check a king with a king in a game of chess.
Yes, in the game of chess, one king can check another king.
No, you cannot put a king in check with another king in a game of chess.
No, you cannot castle in chess if your king is currently in check.
No, you cannot castle when your king is in check in chess.
Yes, in the game of chess, a king can put another king in check.
No, you do not have to say "check" before taking the king in chess.
If you don't say "check" in chess when putting your opponent's king in danger, your opponent may not realize their king is in danger and may not make a move to protect it. This could lead to confusion and potentially unfair gameplay. Saying "check" is a common courtesy in chess to alert your opponent that their king is in danger.
A founded check is when a piece in the middle of the king and the piece moves away.
Yes, a pawn can put a king in check in a game of chess by moving diagonally to attack the king if it is in its path.
Yes, in chess, it is customary to say "check" when putting the opponent's king in danger.