How stock market activities affect/benefit the economy of the country?

For meeting out the financial gap, a company issues IPO and collects money thru the issue , I understand . But in stock market one buyer and one seller transacts between themselves and profit / loss is being enjoyed by them only .How this benefits the economy? To add, the brokers earn brokerage thru this transaction . what is the link between the stock market activities and the economy of the country ? Moreover NSE AND BSE are also pvt ltd, isnt it ? Pls , I want to know the entire cycle Explain

When the market is at it’s upbeat sometimes it attracts money from out side for iinvestmentin industries.