Ysummary is intended to replace the current YouTube homepage.
Right now, most of the homepage, or at least most of my homepage, is filled with recommended videos and channels with a channel I'm actually subscribed to sprinkled in here and there.
I don't want to have my homepage flooded with reaction videos just because I accidently clicked on a reaction video 2 weeks ago. As it is now, I have to click on my subscriptions to actually see what the channel recently released if it doesn't happen to be on the homepage.
Ysummary only shows channels you opt in to either through subscribing through YouTube or following them on ysummary. This is useful if you're interested in what a channel produces but don't want to subscribe for one reason or another.
At some point, things like tags and categories will be added to make it easy to filter the type of content you're in the mood for.
Work in progress