What is poker tells?

A “poker tell” is any clue, habit, behavior or physical reaction, that gives other players more information about your poker hand. The following are tips and you can apply against novice or advanced players. Remember, in poker game there are many contradictions and exceptions to the rule. Also, experienced pros will give out false tells to fool players.

Watch the Eyes
This is why many pros wear sunglasses or visors/caps when playing poker; they know that the eyes rarely lie.

Facial Expression
Again, many pros try to disguise their entire face by wearing a cap and looking downward. This is to avoid the classic stare-down that poker pros are famous for. They may try to study your face for nervousness (detecting a weak hand), or even look for repetitive characteristics like a body "tic". You may have obvious unhappiness in your face when your hand is weak, and conversely, you may show a contrasting show of confidence when your hand is strong.

Weak is Strong/Strong is Weak
In its most simplistic form, this usually applies to novice players but frequently applies to pros as well. Basically, poker players like to be actors, and when they have a monster hand they tend to look disinterested. Repetitive Betting Patterns.

Betting habits
Usually the most revealing poker tells are based on the way a player habitually bets during particular situations. For example, maybe the player always checks when he has made the nuts, or a player may regularly fold after being re-raised.

Online Poker Tells that You Need to Know

Playing poker games online, such as Texas Holdem, you need to know some basic but rather useful poker tells to increase your chances of winning the game. Here are several of them. Seriously pay your attention to them and keep them in your mind next time you are engaged in the game, you will find them really paying off.
1 Fast Check
This is a very common online poker tell. When a player instantly checks, he has probably clicked the "auto-check" tool featured in all online poker rooms. This means that before you have even bet or checked, he was planning on checking. Most of the time, you'll be able to steal the pot with a reasonable bet. However, some players might try to use this tell against you so you should be careful with it.
2 Wait and Bet
When a player waits and bets in poker games online, he usually has a legit hand and is probably thinking of how much to bet which almost always results in the timer running slightly slower than normal. You'll notice this if you pay close attention to the time a player takes to bet. If they wait a long time and check instead of bet, they are usually trying to make you think they have a hand. If that's the case, you can probably take the pot right there.
3 Betting Patterns
Betting patterns are extremely valuable in any variation of poker games. You always want to figure out how each player bets when he has a hand. Most players will give away their cards simply by betting different amounts. For example, if a player raises $50 pre-flop and then only bets small on the flop, he's almost always weak. Notice how hard players raise their aces as opposed to their jacks.
4 Fast Bet
When someone quickly bets, they're almost always trying to scare you. When I want someone to fold, I bet really fast. It shows them strength and is a very intimidating tactic to employ.
5 Telling You Their Hand
Players telling you their hand is a funny type of tell. I've figured out this tell from most of my friends telling me they were lying in the first place. It's also common sense. According to one of my Hold'em rules, when a player tells you his hand without you asking, he's almost always giving away false information. Think about it. Why would he tell you his hand if you didn't ask him? The reason he tells you is to get inside your head and make you think you folded the winner.