The hair or fur of our cat varies in length and colour depending on its race. However, in any race, it accomplishes the same function.
Beneath the fur, cats are covered by fat acids, which are segregated by their glands and spread all over their bodies. This protects them from cold and hot weather and grants each cat with its own specific smell. This specific scent is used to mark their territory after rubbing themselves against a surface or even against us.
We need to point out the specialized hair they possess; their whiskers. These are tactile sensors which allow them to get information of their environment. They help cats when they are hunting their prey and need to be stealthy.
Cats shed/moult their hair or fur during spring and in autumn. In spring, they will change to a finer fur for the summer and in autumn, they will change to a thicker hair to prepare for winter.
Cats which don't come out of their homes might be shedding/moulting hair all year long, due to the heaters at home or any other condition at home which alters their system.
During the shedding/moulting period, we will never see any bold spots. It is a gradual process. If you see a bold spot, it is more likely a sign of an illness.
A healthy hair will come in a form of a shiny and soft fur. This is a result of our cat being well fed and in good health.