The purpose of Texas Holdem Blinds is to guarantee their is money to be won every hand and create action. They take the place of antes used in other poker games. Blinds are bets made without looking at the cards first, hence the name blind.
The typical rule is for the big blind to be the size of the minimum bet for that particular game. The small blind is usually one half the size of the big blind. The player directly to the left of the dealer button will put out a small blind and the next player to the left will be the big blind.
Any combination is possible, the most common is One big blind and one small blind.
The small blind being half or one third the size of the big. Other common blind structures are.
One big blind
Two big blinds
Two small blinds
Two big blinds and one small.
Note in a Tournament the blinds will get bigger as time goes on. In most cash games they stay at the same level.
The Texas Holdem Button, also known as the dealer button or just the button, is used to represent who will be dealing. Since most games use a professional dealer it's generally used to keep the betting order correct.
Make yourself at home. There is plenty of free texas holdem information on this site.