It is known as a good-morning because of the movement in the erector spinae which resembles the bow that traditionally begins a schoolday in some East-Asian countries.
Bent knees can shift the weight forward, which allows the pelvis to drift back further as the body hinges in hip flexion.
Properly applied, it can also strengthen an individual's deadlift; for this reason, it is a key exercise in the conjugate method of training this lift.
The movement can also be performed with an empty bar, a broomstick, or one's body weight, a variation suitable for beginners, casual stretching, warmups, warmdowns or endurance training.
A similar exercise and easier alternative for odd implements such as dumbbells would be doing stiff or straight legged deadlifts.
Famously, Bruce Lee seriously injured himself while performing the exercise after an inadequate warm-up and over confidently selecting his working weight.
At the bottom of the range of motion, this keeps the chin up and the head tilted back, facilitating a flat or slightly arched spine.