Final answer:
The chief difference between original main motions and incidental main motions is that original main motions introduce a new topic for discussion, whereas incidental main motions deal with immediate procedural questions related to the business at hand.
Step-by-step explanation:
The chief difference between original main motions and incidental main motions lies in their purpose and timing within a parliamentary procedure. An original main motion introduces a new subject for the assembly's consideration and is typically made when no other motion is on the floor. On the other hand, an incidental main motion arises incidentally and is needed to be decided immediately due to a question that pertains directly to the business at hand. For instance, a question of consideration might be an incidental main motion that questions whether the assembly should consider a previous motion at all.
It is essential to understand that incidental main motions deal with questions of procedure that arise out of other motions or the business being conducted, while original main motions are put forward to bring a new topic or issue before the assembly. Moreover, incidental main motions must be decided before business can proceed, whereas original main motions establish what the assembly will focus on and discuss.