Buying and Selling
Financial market is a mechanism that allows people to easily buy and sell (trade) market instruments at low transaction costs and at prices that reflect efficient markets. Financial markets have evolved significantly over several hundred years and are undergoing constant innovation to improve liquidity.
If you believe value of a market instrument is going to increase, then you would buy the instrument and at one point in the future you would sell it for a higher price. This is the basic motivation for trading on financial markets.