A buddy is an experienced colleague who is not the new hire's manager. The buddy answers the small questions you would not want to spend the manager's time on: Where do people sit at lunch? Who knows about invoices? How do we write to customers here?
The arrangement works best when the buddy has time set aside and when it is clear how long it lasts. Three months is a good starting point.
A buddy does not replace training. But it makes it easier to apply what was learned in a course, because there is someone to ask when it needs to be used in practice.