"Promote" allows you to move a component (ipt or sub-iam) "UP" within the structure. For example, I could move a bushing from my detailed weldment/asm up to my final asm if I wanted it to be shown in the BOM at that level rather than earlier in the assembly process. The effects? Well, you generally lose all constraints on the object - or anything that was constrained to that object. The same principle applies to "Demote".