What is the difference between combining prayers and shortening them?

The rulings regarding shortening (qasr) and combining (jam') prayers differ. Shortening is reducing the four-rak'ah prayer to two rak'ahs during travel, and its ruling is a confirmed Sunnah, and it is better than praying the full number of rak'ahs. Combining, on the other hand, is joining the Dhuhr and Asr prayers or the Maghrib and Isha prayers at the time of one of them. It is permissible for a pilgrim and for others when there is an excuse, such as hardship, illness, rain, or being occupied with work that cannot be postponed. The reasons for combining prayers are broader than the reasons for shortening them; shortening is exclusively for travel, whereas combining is permissible during travel and for a non-traveler if there is a need or an excuse.