Definition of lay-down
The expression "lay-down" in English means that you put your hand down. An "big lay-down" is a fold that a player makes with a very big hand. If you lay down a pair of checkers preflop against 4bet for example, it will be called a big "lay-down". A lay-down means that you discard your cards, don't call the bet, and give up the main pot (also known as a fold). The fact of folder saves us from having to pay a bet, but eliminates us from the hand. If a player fold at any point in the hand, he loses his right to the pot, even if he fold at the river after having invested a lot of money in the pot.
Knowing how to make a lay-down
lay-down is one of the most important games in poker. It's probably the most unpleasant game to play, but it's a game that you will play at a very high frequency. Knowing when to bluff is a quality. Knowing when to call a bet is a quality. But knowing when to call a hand is an even better quality. The action of folder is probably the action you do most at the poker table. You need to know when folder is at the right frequency, without being exploited. As they say, 1 euro saved is 1 euro won.