Public Share? / Writeable?
These two values specify access controls. There are four possible scenerios:

Public Share 
Writeable 
 
No No Only Authorized Users/Groups can read the share, and only Writeable Users/Groups can write to the share.
 
Yes No Anybody can read the share, but only Writeable Users/Groups can write to it.
 
No Yes Anybody defined in Authorized Users/Groups can both read and write to the share.
 
Yes Yes Anybody can read and write to the share.