The main components of the stock trading is trader,broker,exchange,SE-BI,banks.
when trader want to place any order it can only done by broker.Behalf of the trader broker execute the orders and make the trades happen. Exchange is the thing which is responsible for Trade Settlements. SE-BI is trustworthy between company and public.Stock Trading is a business till the trader have the knowledge of risk vs reward otherwise it will be gambling.
Trader can create Long position if assume the price may go up and create short vice versa,there three types of trading Intraday, Positional, Optional. Based on the trader interest trading can be done.Trading also reflects the company performance due to the financial commitments.