YouTube allows to add managers for your channels to manage videos for your brand and do basic activities like upload videos, add/change titles, descriptions, tags etc.
It is a huge time saver when you have multiple members working on your team producing video content, rather than sharing video files, it can be directly uploaded to your YouTube studio by your manager with not publicly viewable permissions like private/unlisted. It can then be reviewed and published.
Steps to add manager to your YouTube studio:
From your YouTube studio https://studio.youtube.com/
Go to settings > permissions > manage permissions
There you will see options for managing Users and do operations like Change roles, invite, and remove users etc.
You will see manage permissions button which opens in a popup like the below one.
Click on Invite new users as marked in the below screenshot with “Manager” role who can manage your videos, upload new videos, edit video title, description, tags etc