Your laptop is a machine, and holds its power in a battery, which is located on the bottom of the laptop. There are vents along the side of the laptop that help to keep the battery from overheating.
NEVER block those vents. Resting your laptop on a blanket, pillow or fluffy towel is unsafe, and can cause the battery to overheat, causing damage to your computer. Make sure your laptop is sitting on a hard flat surface, and that the vents are not blocked.
Whatever your laptop is sitting on will also heat up, and tabletop surfaces can be damaged by the excess heat.
To be safe, consider using a trivet, hot pad or perhaps a ceramic tile to rest your laptop on, so that any excessive heat does not damage your desk or tabletop.