Answer:
To rule everything in Japan.
Literally
No joke.
But they also didn't really mean much.
On utube, they have this channel called extra history and they have a series called senjoku jedie or something about ancient japanese history about ninjas, and samauri. They didn't even have emperors and had clans which would fite like every day so this guy oda nobunaga actually managed to unite most of Japan before he kicked the can so...
They had a shogun but since there was clans, there was no point of the shogun since they had very little power, and the person who controlled the shogun, theoretically controlled all of japan.
Step-by-step explanation: