What are the regulations for investing in the stock market, and is it forbidden, and if so, why?

It is permissible to buy and sell shares if they belong to companies engaged in permissible activities such as agriculture, real estate, or industry. The price must be paid immediately to avoid selling debt for debt. Companies dealing openly in prohibited things like alcohol or usury are excluded from this permissibility. However, if companies are compelled to deposit their money in banks for safekeeping, it is permissible out of necessity, provided that the usurious interest is disposed of. Companies must refrain from operating their factories with usurious loans.