All cats like to scratch and dig their claws into things. This is just a natural characteristic of cats. It's as natural for them as eating and sleeping. The scratching action is good for a cat's physical and mental health. A good cat owner will provide something for the sole purpose of a cat's scratching. Without one, your carpet, furniture, and walls will be in danger of being remodeled with claw marks and damage.
There are many different things that your cat may like to scratch. Most things made out of wood or carpet can be appealing for most cats. Scratching posts, scratching trees, and various scratching toys are available in most pet stores and on many websites. A base item for scratching won't cost you a lot of money and you can always upgrade to a nice scratching tree or post in the future.
If you do purchase (or build) a scratching post or scratching tree, make sure it has a wide and secure base on it. This will ensure that it remains standing while your cat is using it. If it falls while being used, your cat may be tentative to use it in the future and might go back to using your furniture.
Some scratching posts are made to lay down on the floor. The nice thing about these is they are in a natural position for your cat to scratch, plus they won't fall over.
An alternative to purchasing something to use for scratching is to make one yourself. This can be a lot more simple than it sounds. Gather some branches or tree limbs and screw them together. This would be a very basic scratching tree but will serve the same purpose of store bought ones. If you are a little more creative you can build an actual scratching post and cover it with carpet. Do some research on retail scratching items to figure out the dimensions that you want yours to be. Another option is a simple wooden log on the floor. A wooden log laying down can be heaven for a scratching cat.
Cats may be very common pets but not all owners understand the importance of a designated area or item for cats to scratch on. For the health of your cat and your furniture, either purchase or make a scratching tree, post, or log. It will be an investment well worth it.