All albums and documents are private by default and no one except the author can access them. The sharing can be done by means of links. The author can create a link and send it to someone.
The album opened by the link has functions defined by the author. For example, there may or may not be 'pick' and 'download' functions. Once the author removes the link, the album will no longer open via the link until the author creates it again.
How to create a photo album and share it...