I'm sorry but this is really the basics of stock market, look here for example :
http://investorsfriend.com/how_the_market_works.htm
The Two Divisions of the Stock Market
The Stock Market can be divided into two major divisions.
1.The Primary Market, which could more descriptively be called the Money Raising Market,...
2. The Secondary Market (or Trading Market) is where investors trade their share certificates with each other. This is the "Stock Market" as we commonly know it. This Secondary (Trading) Market is the one that garners almost all of the media attention.
When a company sells a share certificate in the Primary (Money Raising) Market, that share might later trade hands many many times in the Secondary (Trading) Market.
In theory, the Primary (Money Raising) Market could exist without the Secondary (Trading) Market. In reality the Secondary Market supports and enhances the Primary Market in a number of important ways:
The Secondary (Trading) Market provides liquidity so that an investor in the Primary (Money Raising) Market can cash out the investment without having to wait and collect dividends over the indefinite future. Without this liquidity investors would be much more reluctant to invest in the Primary Market and if they did they would want a bigger expected return. The cost of raising money would be much greater. Many companies would never have been able to raise money. In short the technologically advanced world that we live in would have been delayed, perhaps for centuries, if there were no Secondary Market. (All hail the Secondary Market!)
The Secondary (Trading) Market provides "price discovery". The fundamental value of any share is the "present value" of the stream of future dividends to be expected from holding that share. The Secondary Market allows investors to vote or bet as to that expected value.
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The Bad News about the Secondary (Trading) Market.
Investors in aggregate always lose money in the Secondary (Trading) Market.
For every trade that is profitable for one investor by buying a share at what turns out to be a bargain price, an equal and opposite loss is suffered by the investor(s) on the other side of the trade. This is in sharp contrast to the Primary (Money Raising) Market where if the fortunes of a company improve, all investors make more money and no investor loses money as a result of a company becoming more profitable. Also, for every share that is traded, a third party makes a commission. <font color=RED>Thus trading shares is ultimately a negative sum game</font>. Investors in the aggregate must always lose money on the trading aspect of investing.
Still, this trading is necessary and supports the Primary (Money Raising) Market. And, <font color=RED>more astute traders will make money at the expense of less astute traders</font>. But all traders should be aware that they are ultimately engaged in a game that is clearly stacked against most of them. The brokers are always taking a commission and traders in the aggregate must always lose.
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That's why the commonly "Stock Market" which is the secondary market which is speculation doesn't add no value since it is a ZERO SUM GAME (and even negative due to commission, slippage ... and market manipulation). From the economic point of view this secondary market is like a Casino.
Quote from trade4succes:
Second hand car dealers don't add value as well then? Well, the economy would be better of without them, or what about meat traders, uh, should I go on, before we know it, there isn't an economy left to discuss about