what does long run n short run actually mean? how can we say that demand is more elastic in short run?
The short run is the period of time in which at least one of your input quantities is fixed, but all others can be variable. The long run is the period of time after which all input quantities are variable. Short run and long run are not fixed time periods, they will vary across companies and industries. As an example, think about a company which produces actuarial textbooks. It would be very easy to buy more paper, and hire more staff, but it would take us much longer to buy another factory to print books. So we could say in this instance that the "long run" is how long it would take us to set up a new factory.
cjno1 nailed it. The only think that I'd like to add is that short and long run varies from one firm to another.
