Most likely it is to cool your CPU or other components of your laptop. Do you know if the heat is coming near the battery, or more towards the screen?
If most of the heat is on the battery, it may be time to replace said battery with a new one.
If you are able to, I recommend cleaning your fans (you will most likely need a screwdriver to do this and this would probably void any warranty you have).
The other option is to by a laptop fan cooler with fans, I used to use one on my older laptop, and it did help keep the machine cool.