Once the cards are dealt, the betting round begins. This round is called “preflop”. Bets are placed clockwise from the left of the big blind. At this time, the big blind corresponds to the opening bet, so the first player cannot check. The small blind player pays the remaining half price to call. If there is no blind, bet from the left side of the dealer button.
If two or more players remain after the preflop betting, the dealer places three cards face up on the table, and this is called “flop”. The three cards are common cards (community cards) for all players. The next bet is made clockwise from the player to the left of the dealer button when all cards are dealt.
At the end of the flop betting round, the dealer opens another common card. This card is called “Turn (or Force Street)”. Similarly, when the betting round in the turn ends, the dealer opens the last common card. This card is called “River (or Fifth Street)”.
If more than one players remaining at the end of the river betting, a showdown will be performed to determine the winner.
If more than one player remains after the last bet, a showdown is performed.
Showdown is to compete for the strength of the hand using the strongest combination of the two cards in the player's hand and the five community cards.
You can use both at hand, just one, or not at all. The player with the strongest hand can win the pot.