Is perpetual check a rule in chess?

No. The Laws never mention it. What actually ends the game is threefold repetition, which the checking side claims, or an agreed draw once both players see it. Five repetitions or seventy-five moves would end it automatically, but nobody plays that far: the position is obvious long before then.

Can you escape perpetual check?

Sometimes, and it is always worth two minutes of checking. The king may have a flight square you missed, a piece may be able to interpose, or the checking piece may be capturable. If none of that works, the attacker has to keep checking, because stopping means facing whatever threat made him start.

Is perpetual check a win or a draw?

A draw, half a point each. It usually feels like a win for the side giving the checks, because that side is normally the one who is losing and has found a way out. A queen giving check every move is not making progress, and a queen alone cannot mate, so the game goes nowhere.

What is perpetual check?

Black has two rooks and two pawns against a bare queen, his opponent’s king is boxed on g1, and the rook on a2 is one move from the first rank. White is losing this in every line. White also draws it, in four moves.

1.Qg6+ and the black king has exactly one legal move, Kh8. Then 2.Qh6+ and again exactly one, back to g8. Neither black rook can reach g7 or h7 to block, and the queen never stands next to the king, so she cannot be taken either.

Look at what the queen is doing. She stands one square away from the king on the g-file, then one square away on the h-file, so the single square between her and the king is the only place a blocker could go, and Black has nothing that can get there. The king has one legal reply each time. After 4…Kg8 the position in the diagram has appeared for the third time, and White claims a draw under Article 9.2.

That is perpetual check: checks the defender cannot escape, forever.

The draw comes from somewhere else

There is no article of the FIDE Laws headed “perpetual check”. The phrase is chess slang for a position, not a rule, and the half point arrives by one of the ordinary routes: threefold repetition if the checking side claims it, an agreed draw if both players can count, or the automatic fivefold rule if two stubborn players keep going.

In practice you will almost never see it played out. One player says “it’s a perpetual”, the other looks for thirty seconds, and they shake hands. Do check first. A perpetual that turns out to have a hole in it is how strong players win games from worse positions.

Checking is not the same as winning

Beginners see a string of checks and assume something good is happening. It usually is not.

White's king is asleep on h1. The queen can check on the e-file, then the d-file, then the c-file, and keep it up as long as she likes, but she can never mate on her own: any square next to the black king is a square he can just take her on.

Four checks, no progress. A lone queen chases a king round the board all day and mates nothing; she needs her own king to cover the escape squares, which is the whole method behind king and queen against king. Perpetual check is a draw for exactly that reason: nobody is getting anywhere.

When to go looking for one

Two moments. The first is when you are losing. Before you resign, count your checks: an exposed king, a queen that can reach two checking squares, and no defender able to reach the squares in between is the whole recipe, and it comes up most often after both sides have castled and one king has lost its pawn cover.

The second is when you are winning, which is when it costs you. Before you grab the second rook, ask what his queen does with a check on g6. That habit belongs in the same list as the rest of your blunder checks. And if you want to train the eye for it, the drawing resources live in puzzles where the best result is equality: half of them are perpetuals, and the other half are stalemate tricks.