The blinds in Texas hold’em are positions that oblige the player to place a bet before getting to see the cards. A blind is often thought of an imposed pre-flop bid, because it is made before getting your cards. You don’t have a choice when in this position and you will have o bet the amount the game imposed for the respective blind. Texas hold’em has blinds because they bring along with them a little more action, even if it is forced. Without having the blinds, it is highly probable that players would simply sit around the table all day and fold every time in pre-flop just because they didn’t get their pocket aces. The initial idea for the blind was to force everyone pay to see their cards and then the whole game would evolve around the battle for that blind money. But today, the blind evolved and in real or online casino, especially in limit games blinds became very popular. They are often referred to the small and the big blind and they are the players placed to the left of the dealer button. So at table it is first the dealer button (or that player that is in dealer position for that game), the small blind and then the big blind.
As a general rule, the big blind is twice the small one. But their actual amount depends on the limits of the game. The low limit stated is exactly the big blind amount. The limits that a game has are the amount of the small bet or the bet on the flop and the bog bet or the bet on the river. So, if you are entering a $5-10 game, then you must know this is a games in which the big blind is $5 and the small blind is $2.5 (it can be either 2 or 3 if the rules allow that but it is constant throughout the whole game).
The games become tighter as the blinds are higher. If in a game of 15$/30$ limits, then the blind will be $15 and $10 – that is almost a big bet already in from the blinds. The game will be played tight, but when it comes to low limits the games are pretty loose because there are many people in anyways. After one hand, the blind change and they follow the betting direction, going clockwise. So if you were the big blind now you will be the dealer, which is the best position.
The blinds structure mentioned above is the most popular one but there are others that can be encountered. For example there are games that have three blinds. The big blind and two small blinds one in the normal small blind position and one in the dealer position. This way the games are encouraged to become looser and looser.