You can create a read-only board to share with clients or people who aren't on Milanote yet. This is a great way of keeping others updated on your work and often replaces the need to create traditional document. Only people with the link can view the board.
People who visit the link will be able to see all the content of the board (and any sub-boards as well) but they won't be able to edit it.
Clicking "turn off" will disable the link you sent out and make your board private again.