A few decades ago, most buyers and sellers were individual investors, such as wealthy businessmen, usually with long family histories to particular corporations. Over time, markets have become more "institutionalized"; buyers and sellers are largely institutions (e.g., pension funds, insurance companies, mutual funds, index funds, exchange-traded funds, hedge funds, investor groups, banks and various other financial institutions).
Warren Buffett is the best example to hit this point home. In 2008, he bet some hedge fund managers $1 million that they wouldn’t be able to make more money in a decade than a cheap, boring index fund. An index fund uses simple investing algorithms to track an index and doesn’t require active human management. Conversely, hedge funds stack management fees on top of trading fees to pay for the time and knowledge actual strategists are putting into your investments.
Learning about great investors from the past provides perspective, inspiration, and appreciation for the game which is the stock market. Greats include Warren Buffett (below), Jesse Livermore, George Soros, Benjamin Graham, Peter Lynch, John Templeton and Paul Tudor Jones, among others. One of my favorite book series is the Market Wizards by Jack Schwager. How Do You Calculate Price and Volume Variance?
Financial innovation has brought many new financial instruments whose pay-offs or values depend on the prices of stocks. Some examples are exchange-traded funds (ETFs), stock index and stock options, equity swaps, single-stock futures, and stock index futures. These last two may be traded on futures exchanges (which are distinct from stock exchanges—their history traces back to commodity futures exchanges), or traded over-the-counter. As all of these products are only derived from stocks, they are sometimes considered to be traded in a (hypothetical) derivatives market, rather than the (hypothetical) stock market.