Share a folder
Open the folder you want to share and click the 'share' icon at the top right. Choose how you want to share it, or copy the link. Always share using this button, not the link in your browser's address bar. Want viewers to request access first? Then set the folder to 'private'.
If you later add a new album to the shared folder, viewers will see that album too. A new album isn't added to a folder automatically: you do that yourself.
Create a folder
Click the 'more' icon (…) at the top right of the album overview to organize your albums into folders.