Stock market participation refers to the number of agents who buy and sell equity backed securities either directly or indirectly in a financial exchange. Participants are generally subdivided into three distinct sectors; households, institutions, and foreign traders. Direct participation occurs when any of the above entities buys or sells securities on its own behalf on an exchange. Indirect participation occurs when an institutional investor exchanges a stock on behalf of an individual or household. Indirect investment occurs in the form of pooled investment accounts, retirement accounts, and other managed financial accounts.
To keep costs as low as possible, famous investors like John Bogle and Warren Buffett recommend buying and holding the entire stock market. Known as passive investing, it is a buy and hold strategy where you buy an entire market index, typically the S&P 500, as a single mutual fund or exchange traded fund (ETF). By buying an entire index, you are properly diversified (have shares in ~500 large companies, not just one), which reduces your risk long term. In fact, John Bogle is credited with creating the first index fund.
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.