If you're reading this article, you're clearly playing the frequent flyer game. Simply put, redeeming and qualifying miles differ in what they are used for. (Note: Airlines may have their own terminology to refer to redeeming and qualifying miles.)
Redeeming miles (RDM) are often what airlines promote to draw fliers in; for example, a credit card bonus can offer up to 40,000 miles to your frequent flier account. These miles are used exclusively to redeem for free flights and merchandise. They are often used promotionally during marketing campaigns and do not count in attaining status with an airline.
On the other hand, qualifying miles, or also known as elite qualifying miles (EQM), contribute to the annual requirement required to reach a certain tier in a frequent flier program. Most of these miles are attained by physically flying. The limits for achieving status often resets annually. Once you reach a tier, you are eligible for certain perks like extra baggage allowance.
In the screenshot below, United uses the term "Premier Qualifying" miles to refer to EQM:
Certain tiers in a program also correspond to status within an airline alliance, such as OneWorld or Star Alliance. These levels are often more useful for receiving perks when flying internationally on different carriers. You will, however, receive the most perks though flying on your home airline.
Qualifying miles can also net you redeeming miles, though the exact percentage depends on the fare bucket that you fly. In a nutshell, your mileage may vary.
