Many times people keep the furniture in their homes the same their entire lives. When you move the furniture you will see small or large indentations in your carpeting from where the legs have not only rested for so long, but have also pressed your fibers together.
Depending on how severe the furniture marks are they will sometimes come out during carpet cleaning but most of the time they will not. There are however a bunch of different tricks out there that can help you get rid of these marks.
For example you as the customer could take a damp towel and lay it over the indentation for a few hours. This will expand your fibers. Then you should take a small brush and try to pull the fibers back to length without stripping them from the carpet backing. Many times what can happen is the padding underneath the fibers may be crushed. If that is the case your out of luck. There is nothing else you will be able to do to fix it.