Although jumping up is a natural behavior for dogs, it can cause problems for humans because they could cause serious damage by knocking that person to the ground. Even small dogs can hurt someone by jumping up.
They have to be taught that this behavior is unacceptable. However, it is helpful to understand why they are doing it.
When dogs are excited, they want to let you know it. It is a great way to express their joy or that they want to get as close to your face as possible to give you some licks. Also, when jumping up on the couch they are doing it to get close to you or to just find a more comfortable place to sleep.
However, jumpy behavior could also be an overreaction to certain stimuli, typically due to fear and anxiety. Observe your dog over a period of days to determine the source of the jumpinesss. The doorbell or vacuum cleaner are common environmental causes.
If your dog is still a young puppy, do not allow the jumping-up-on people habit to start because it can be challenging to recondition a dog who has been doing this his/her whole life.