What is The Stock Market?
It is by definition a market in which shares of companies stocks are bought and sold. When companies start growing they need to find investors willing to invest on the company. They need to rise money to keep buying machines and products and to expand their businesses.
At the same time many investors want to find companies where they can invest their funds, so they can receive passive income from the growth of those companies, which usually cause a growth on their portfolio of invested funds.