Blinds
Two forced bets posted before the cards are dealt: the small blind and the big blind. Without them nobody would have to put money in and there would be nothing to play for.
Blinds are two bets that two players post blind, before they see their cards. The small blind posts half a unit, the big blind a full one, and the unit names the stake: at NL100 the big blind is one dollar. A hand starts with a dollar and a half already in the pot, and everyone else has something to fight for.
The duty goes around the table: over six hands each player posts the small blind once and the big blind once. Over 300 hands that is about 50 rounds and roughly $75 in forced bets from each seat. Half the money that passes through the table in a session starts as somebody's blind.
Why everyone loses from the blinds
You put money in before seeing your cards, and after the flop you act first, before everyone else. Both seats are the worst at the table, and skill does not change that: every player in the world loses from the big blind; the only question is how much. In session 7 the big blind cost me $84 in half an hour against an overall result of +$6: the other four seats earned that loss back.
Hence the only job in the blinds is to lose less than the norm, not to win. The big blind is worth defending because the dollar is already in the pot and a call is cheaper than it looks, but defending it too widely is the second most expensive mistake in cash games after overpaying on the river.
The same in business
A blind is the price of a seat at the table: rent, a licence, payroll in a month with no revenue. Everyone pays it, pays before seeing the cards, and the winner is not the one who avoids it but the one who pays it less often than he earns. A business that counts only its good deals and not its forced bets is surprised at year end about where the money went.
The whole hand is in session 7: “Don't pay more for an answer you were offered cheap”.
The other terms are in the glossary.