What is a stock target price? How long it is valid?

Stocks as I explained can be traded for short term i.e. intraday or for long term, more than intraday; maybe weeks, months or years. Person A buys a stock XYZ for a price of 250 INR. Now since the stock is bought he needs to sell that stock for a price more than 250 to earn profit. Suppose he feels that market is good and he thinks the stock might go up-to 275, then he puts an order to sell the stock for 275. When the stock price reaches 275, his stock gets sold. Meaning he achieves his target price. The same applies to selling a stock (short sell) which I have explained below.