If you have bought 50 stocks of some company on delivery basis, these stocks will be transferred to your Demat Account (usually it takes 2-3 days to complete the transfer) and you can do whatever you want with the stocks.You can keep them for 5 years or sell them the next week.

In Intraday trading stocks are not actually transferred to your account and you have to square off your position before the market close on same day (sell same no. of stocks)