Entries are Important

Entries are the means of getting from one hand to the other. When a card wins a trick you have gained entry to the hand. You have won the ability to lead out of that hand.

For Example

You are North South in the deal below.
In a 4H heart contractThe final suit and level of bidding sets the number of tricks and the trump suit for the game.This is called the contract. The partnership that wins the bidding can earn the points if they succeed in getting the number of tricks they contracted.
The number ..., the spades in dummyThe declarer's partner is called the dummy, and after the opening lead has been made by the opposition dummy lays all their cards on the table face up.
That is the end of this game for dummy and they have no more to play in this game.
Declarer now plays ... are high, you have no way of getting to dummy to play them. You will end up trapped in declarer’s hand leading out your low diamonds for the opposition to win. You need Entries.

The contract is 4H and South is DeclarerThe player who during the auction made the first bid the SUIT of the final contract, becomes the declarer.  The also play their partners hand which  is now renamed 'dummy.'
Declarer plays both their own and dummy's hand.

The Process

South is declarer and hearts are trumpsA suit of cards with the highest ranking over the other suits in a particular hand
Noun usage - A card in the trump suit whose trick-taking power is greater than any other suit card.
Verb usage - To play a trump after a plain suit has been led or otherwi....The declarer has a good chance of winning 13 tricksA round of 4 cards where each player contributes 1 card. There are 13 tricks in a game of bridge. on any lead if they plan their entries.

• The Opening Lead is a Club
• Win with the AC in Declarer’s hand
• Play only two rounds of hearts.
• Lead out the 3C and ruffAnother word for trump a way to win a trick and it means to play a trump card on a trick when that player has run out of the suit which was led. If trumps were the suit led then following suit and playing a trump card is not 'ruffing' its following suit with 4H in dummy – this is the entry play.
• PLay the three top spades in Dummy discarding Declarer’s losing low 7D, 6D, and 5D cards
• Play a low diamond from Dummy to AD and play KD
• Lead out your last round of hearts dropping East’s outstanding 7H
• The rest of the tricks are yours

Notice that Declarer didn’t play all the 6 winning spades because they were anxious about being ruffed by the outstanding trump card.

To develop your entry in this game you had to arranged to drawDrawing - refers to the process of leading a suit multiple times in order to deplete the opposition  holdings in that suit -  in other words its to draw out their cards in that suit. the term refers to to either the trumps or to side suits trumps but not all of them! In this case One trump is still out but firstly you need to ruff to enter dummy and play your winning spades.

Remember, the main way of avoiding losers is by establishing and playing your long suits.