The stock market is the term we use to refer to the collective marketplace where stock securities are exchanged for agreed upon prices. The stock market as a whole is actually a collection of loosely tied together exchanges which facilitate the actual trading. When most people in the United States think of the stock market, they think of the New York Stock Exchange with hundreds of brokers screaming to buy and sell securities rapidly throughout the day. While this may have been how all the stock trading was facilitated in the past, today improvements in technology have vastly changed the landscape in which buyers and sellers interact.
Today most stock volume is transacted over electronic communication networks which are publicly viewable electronic exchanges, also called ECNs, as well as in dark pools, which are another form of electronic trading where the buyers and sellers are hidden until an agreed upon price is matched. These various exchanges and dark pools are tied together through quoting systems to form the order book of a stock. The highest bid (coming from any exchange) and the lowest offer (also coming from any exchange) make up the national best bid and offer. It is now illegal for most transactions to occur away from the national best bid or offer (NBBO), so even though the market is fragmented amongst various exchanges, a retail trader is still guaranteed the best price possible at any given time. There are some exceptions where institutions may trade with each other away from the NBBO but this isn’t of much concern to any day traders.
The true purpose of the stock market is to allow corporations to access private wealth in order to make investments to grow their companies. The benefit to private wealth is that when they invest in a company that grows, they realize the appreciation in value of that company by holding securities that increase in value. So fundamentally if a company makes more money, and has expectations to make more money in the future, the price of the companies shares should go up. As any market participant knows the correlation between earnings and share price is less than perfect, especially in the short term.
Of course from the way the market is structured, and the ease with which buyers and sellers can interact, traders are able to take shorter term positions in hopes of profiting from near term volatility. The value or detriment of trading volume as compared to purely investing volume in the stock market is always being debated, but of course as long as it is legal you can count on a significant amount of total orders to be for the purposes of taking trades.
Participants in the stock market range from small “mom and pop” long term investors to high frequency trading hedge funds whose trades are directed on microsecond time frames with super powerful computers and algorithms. Today for better or worse most volume is transacted by high frequency operations. Some of this is a necessity to navigate the fragmented markets with large orders, while other volume is very predatory on small inefficiencies in price. There is also a substantial amount of volume transacted in dark pools, so it would behoove any prospective trader to really understand what these are, how they operate, and how they are used.
The stock market as it exists today may be unrecognizable to past generations given technological advances, but it is none the less thriving as volume continues to generally increase year over year.