A personal tag can be created by any employee on the tags page by going to the Settings menu (your profile in the top-right corner) and selecting the Tags section.
Any business unit manager can create a public tag. It is enough simply to create a personal tag and convert it to a public one, after which the public tag will be visible to all employees. To do so, on the tags page, select the required tag and click Make this tag public on the Tag type icon to the right.
Public tags differ visually to personal ones—a special icon is located next to the name of a public tag.