The stock market refers to the collection of markets and exchanges where regular activities of buying, selling, and issuance of shares of publicly-held companies take place. Such financial activities are conducted through institutionalized formal exchanges or over-the-counter (OTC) marketplaces which operate under a defined set of regulations. There can be multiple stock trading venues in a country or a region which allow transactions in stocks and other forms of securities.
IMPORTANT – Like paid subscriptions, be careful with classes and courses. Most are easily over $1,000 and are sold with false promises to acquiring valuable knowledge. Their fantastic sales funnels will suck you in, take your money, excite you during the course, then leave you with a strategy that wasn’t even profitable to begin with. See, 10 Things I Wish I Knew About Trading Before I Got Started.
Investor Protection: Along with wealthy and institutional investors, a very large number of small investors are also served by the stock market for their small amount of investments. These investors may have limited financial knowledge, and may not be fully aware of the pitfalls of investing in stocks and other listed instruments. The stock exchange must implement necessary measures to offer the necessary protection to such investors to shield them from financial loss and ensure customer trust.
When you've been approved for margin stock trading, you're also eligible to short stock. Almost every successful stock trader has shorted stock at one time or another. When you short stock, you make money when the company's shares fall—or, even better yet, when they crash. The problem is that you can expose yourself to unlimited liability when you do this. 
As a primary market, the stock market allows companies to issue and sell their shares to the common public for the first time through the process of initial public offerings (IPO). This activity helps companies raise necessary capital from investors. It essentially means that a company divides itself into a number of shares (say, 20 million shares) and sells a part of those shares (say, 5 million shares) to common public at a price (say, $10 per share).