Stock exchanges are regulated by SEBI
Stock exchanges appoints stock brokers
People buy/sell stocks using brokers platforms
Stock trading can be long or short
If people thing that price of the stock will go, they will buy and then sell the stock. This is called as long
If people thing that price of the stock will down, they will sell and then buy the stock. This is called as short
If trade is squared off in a day, it is called as intraday
If stock is taken on delivery and kept for few days/weeks it is called is positional