1. Private investors play a vital roles.
2. Funds and institutions.
Traders of all backgrounds participate and it's vital to pay attention to see who is ready to pounce.
Stock market works like any other market, it just matches demand and supply and and makes sure that buyers and sellers come together to "exchange" their shares and try to find the best value for their money.
There are many reasons to it. But the main reason is money... Traders and investors are constantly on a look-out to find the next big thing.
Finding the value is the ultimate goal.