I'd be worried if it stopped and couldn't run... It depends on the machine's design and which fan you are talking about. It doesn't take much to heat up a PC when it is running a few programs, and needs a good airflow. Some fans are setup to run at different speeds depending on "load".
As it is a Laptop in your case; it will have restricted airflow and heat faster than a Desktop so typically the fan will constantly run.
it depends on programs if you running more programs then it will run very fast and generate heat but if you are using a single or two programs then its running not so fast if you have some problem regarding fan then you should go to nearest laptop repair shop and repair your fan
Wrong, there's lots of reasons why excess heat is generated, saying it's down to how many programs you have open is incorrect. If you have programs running idly in the background for example it'll use no extra cycles and thereby generate no excess stress.