Checking, betting, calling, raising and folding

Check - A bet of zero dollars. By checking, a player retains the right to call any bet made by a player who acts after he does, or even to raise if a bet is made.
But if someone's already bet when it's your turn to act, you can no longer check, and must either fold out of the game, call the bet, or raise the bet.

Bet - A wager of a curtain amount of money by a player in a poker game. This term is normally used to describe the action made by the 1st player that makes a wager in a betting round.

Every table will have a set stake limit which will determine the increments in which bets and raises are made. i.e. on a £2/£4 table, bets are made in increments of £2 and £4 respectively.

Call - To equalize the amount bet/wagered into the pot. This would be equivalent to the largest bet placed on a table by one player.

Raise - To increase the amount bet/wagered by your opponent

Fold - To decide not to bet, call or raise. By folding, a player relinquishes his interest in the pot

Ante - A token sum of money contributed by each player before the cards are dealt.
Antes are used in Seven-Card Stud, Seven-Stud/8 and many other games.

Blind Bet - A forced bet by one or more players before the cards is dealt. This takes the place of an ante. The requirement to post a blind bet rotates around the table from hand to hand along with the dealer button, so that each player pays his fair share.

Blind bets are common in Hold'em and Ohmaha as apposed to Antes which are used in Stud games.

In most casino games, there are 2 blinds:
Small blind = half small stake amount
Big blind = small stake amount

i.e. on a £2 / £4 stake table, the small blind = £2/2 = £1 and the big blind = £2

These bets are called "blind" bets because they are posted before the player sees his pocket cards and they are also considered "live", which means that players who post the blind still have an opportunity to raise when the action gets back around to them.

Stakes, Fixed limit, pot limit and no limit

Every poker table has 2 stake limits, which dictates the minimum bet and raise amounts allowed for the various betting rounds. Bets and raises are also made in increments of the stake amounts.

There are 3 types of limits that apply to the maximum amount that a player can bet or raise by, in any betting round of poker:

Fixed Limit - The maximum amount that a player can bet or raise by in any fixed limit game, is equal to the stake limit for the betting round in which he is playing.

No Limit - In No Limit games, there is no limit to the amount that a player may bet or raise by; however, the player will still be limited to the total amount of available funds at the table at which he is playing.

Pot Limit - The maximum amount that a player may bet or raise by in a pot limit game, is equal to the amount that a player wagers in order to call a bet (if a bet has been made) plus the total collective amount of all the wagers made into the winning pot.

Position

A players' position in a poker game is calculated relative to the dealer button, or the first player to act in a betting round of poker.

Early position would be the players that are closer to the first player to act in a betting round and late position would apply to players who are closer to the player that is last to act in a round of betting.

In poker, position means power. It is almost always advantageous to be in late position and act after you've had the benefit of seeing what your opponents do. Their actions provide clues about the real or implied values of their hands.

This is true in every poker game and is particularly important in fixed-position games, like Hold'em and Ohmaha. In these games position is fixed for the entire hand, unlike Stud, where it can vary from one betting round to another.