Stock order placement for buy or sell through online platform given by broker.
Demat account needed to perform trading and exchanges will exchanges the order between buyer and seller.
Every order has a settlement date and if it intraday settlement is in the same day for positional it is T+2 days.
Long position is created when buyer expects the price to go up and short position is created when a stock price is expected to go down.
Any trade return should be more than risk else it is called as gambling.