As you know samba is used to share Linux machine, so that it can be visible when accessed by Windows machine (CMIIW), making Linux become a good File Server in a mixed network environment. Anyway as a file server we cannot just give the access to everyone to “see and access” all the folder inside it. I bet you still want to have some privacy for your self.
Authentication in Samba comes in several ways, but what we are focusing is on the mixing of share and user level security. In user level, the user need to input some credential BEFORE the user want to “see and access” what file available in that share. While in share level, the user can see all the file but then, the user need to put some credential if they want to access the file (each file or folder has different password) So what we want to do is to have user-level security on your Samba server, but we want Windows clients to be able to see a list of shares on the Samba server without authenticating, like a share level server.