Stocks are a small part of an underlying company. A stock or a share, as it is differently named reflects how valuable a company is. Public companies only are available for trading.
The value is determined by many factors, one of them is how often people are trading (buying and selling) its shares. Stocks do not have a static price, it moves continuously depending on the internal and external factors, each second of the day. Internal issues like management, new products or services released, and external factors like government tax policies, international trading restrictions, new competitors with better products, ect.
Traders are able to trade stocks in many stock exchanges. There are different stock exchanges all over the globe and they operate at different times during the day. For example, if you trade stocks in the New York Exchange, you will be able to trade during 9:30 AM to 4:00 PM Eastern time. Most trading activity takes place during this time, even though there are pre-market and after-hours trading time available. To find and trade your favorite stock, you need stock’s ‘ticket’. If your favorite company is public, you can search it by the name followed by the term ‘quote’, and you will get the ‘ticket’.
The secret is to find the right moment when to buy and when to sell the stock. You can buy at a moment when you think the price is quite low, and you expect it to grow. Once you see that the price reached a peek, sell the stock and make the profit out of the price difference. This way of buying and selling stocks in a relatively short period of time is called short-selling.