I saw that episode (I guess it's the same you are referring to) and they were playing exactly five card draw.
5 Card Draw Rules and Game Play
Five Card Draw is one of most basic forms of poker, and it's the kind of poker you're used to seeing in movies and on TV.
Because the game has been around for such a long time, and has been played in countless home games and card rooms across the nation, there are a couple different variations on the traditional rules. Below you will find all of the most commonly used rules for playing Five Card Draw.
The game is simple: make the best 5-card poker hand possible after one draw, and bet accordingly. The player with the best hand after the second betting round takes the pot.
Blinds and Antes
There are two main ways to play 5-Card Draw:
1. Ante
2. Blinds
The ante method is the original way the game was played, and is most commonly the system used in home games around the world. In this version each player must pay a predetermined ante before being dealt any cards.
In the second system, the game functions as a blinds game, similar to Texas Hold'em. In a blind game, only the two players to the left of the dealer must pay money before the cards are dealt.
The player to the dealer's immediate left pays the small blind, while the player to the left of the small blind pays the big blind.
Although the blind amounts can be set to any amount you like, the small blind is typically half of the big blind, the big blind being approximately 1/100th of your total buy-in.
The Deal
Once all players have anted (or the blinds have been paid), the dealer deals every player (starting on his left) five cards face down.
After all players receive their five cards, the first betting round ensues. If you're playing with blinds, the betting will start with the player to the left of the big blind (same as Hold'em), while if you're playing with antes, the betting must start with the player to the left of the dealer.
In an ante game like this, the first player to act is allowed to check (meaning they are not forced to bet, and can choose to stay in the hand for free).
For more information on the rules and specifics of how a betting round functions, head to Texas Hold'em Rules and Game Play.
The Draw Round
When the betting round completes the draw round begins with the player closest to the dealer's left. Assuming this player hasn't already folded, they have the option of changing any amount of cards they choose.
A player can "stand pat", meaning they keep all five cards, or they can throw away any amount from 1-5 cards, getting them replaced with an equal number of cards from the top of the deck.
In some home-games and rule-sets a player may only exchange up to a maximum of three cards. This rule is typically used only in home-games as it only benefits the weaker players. It is almost never correct to call in the first betting round, only to throw away four or all five of your cards.
The Second Betting Round and Showdown
Once all players have received their new cards, each player must evaluate their hand and proceed to the second (and final) betting round. Once this betting round is completed it's time for the showdown (assuming more than one player still has a hand).
Just like almost every other form of poker, the player with the best 5-card poker hand at showdown wins the pot. Head here for a complete list of poker hand rankings.
Once the showdown is complete, the dealer collects all the cards, and passes the deal on to the player to his left.
Source: pokerlisting
Hope this help