In a Texas Hold' Em poker game, the kicker is the weaker of your two initial cards that you get dealt in your starting hand. It tends to apply most if your stronger card is an Ace.
For example, If you're dealt A-9 then your starting hand is Ace high with 9 kicker. If you're staring down at a miserable 7-2 then it's 7 high with 2 kicker, and so on.
Over the years I've played poker, I think one of the most common mistakes I've noticed is players (including myself) ignoring the kicker, or at least not giving it enough thought.
On a 10 seat table there is a reasonable chance of more than one player being dealt an Ace. So if you're dealt an A-6, chances are another player is holding an Ace and it's probable that he has a stronger kicker than a 6. A lot of players overlook the kicker, perhaps raise, then get excited when the flop produces another Ace, giving them top pair. Remember, your opponent will also have top pair and with a probable stronger kicker and is therefore ahead. You are depending on catching an unlikely card on the turn or river to win the hand.
I'm not saying never play your Ace-low kicker. Like most situations in poker it very much depends on the particular situation. If there's 10 players at the table and you are first to act, you might consider a check or fold. If there's only 2 or 3 opponents then it's still a strong starting hand, as statistically you're likely to be the only one with an Ace.
Top players frequently have the discipline to fold Ace-rag, as it's known for very good reason!
Good luck at the tables.
