I was reading up on Gao Wei, the emperor of Northern Qi and got curious about the process of reign and having imperial power. For instance, Gao Wei passed the throne to his son, but he became Taishang Huang (since he's still alive and haven't given the throne to his son because he's dying). Naturally, you'd think his son gets a shot at being Emperor and being able to make decisions on his own. But it is said after Gao Wei became Taishang Huang and his son became the new reigning emperor, Gao Wei still has imperial power. So what's the point of giving the throne to your son, if you're still going to do the job? I don't get it.
Someone please explain this to me. Does it imply that the new emperor can make decisions, but his father the Taishang Huang can still veto his decision?