Q:

What is the purpose of a Windows Workgroup?

In Microsoft Windows, what is the purpose of a Workgroup? I understand that a Domain allows the administration of security (user names, passwords, file access, etc.) to be centralized. But what does a Workgroup give you?

A:

Workgroups just provide a grouping when browsing resources in the UI.  "Network Neighborhood" (which has gone under a variety of names, such as "Network Near Me") displays computers that share your workgroup name.  And there's an "Entire Network" that lists all the other workgroup names.
There's no impact on security or resource access.  It's just a display thing.

A:

After some doubting whether to post it as a separate question being closed as duplicate of this question, I decided to put it as answer... 
Any corrections and explanations of contrary point oа view are welcome.  
I either disagree with accepted answer that 

In computer networking, a workgroup is a collection of computers on a
  local area network (LAN) that share common resources and
  responsibilities. Workgroups provide easy sharing of files, printers
  and other network resources  

or do not understand the basics of identification, network sharing and access 
In my LAN I have 8+ workgroups + Windows-based laptops having arbitrary set workgroup names and this, workgroup naming,  does not have any influence on visibility or accessibility of computers.   
IMO, workgroup naming is just a convenience permitting to see computers in different "folders" on Windows Explorer.  
In a workgroup the resources (shared folders, network printers, services, etc.) are identified by 

(SID computer name)\username\   

without involvement of any workgroup names.
prepending them and there is no workgrup name used.   
Or is it?
What have I missed?    

A:

In computer networking, a workgroup is a collection of computers on a local area network (LAN)  that share common resources and responsibilities. Workgroups provide easy sharing of files, printers and other network resources. Being a peer-to-peer (P2P) network design, each workgroup computer may both share and access resources if configured to do so.

Perhaps a little bit of Microsoft Windows history would help building the context,

Windows for Workgroups is an extension that allowed users to share their resources and to request those of others without a centralized authentication server. It used the SMB protocol over NetBIOS.

so,

The Microsoft Windows family of operating systems supports assigning of computers to named workgroups. Macintosh networks offer a similiar capability through the use of AppleTalk zones. The Open Source software package Samba allows Unix and Linux systems to join existing Windows workgroups.
Workgroups are designed for small LANs in homes, schools, and small businesses.
A Windows Workgroup, for example, functions best with 15 or fewer computers.
As the number of computers in a workgroup grows, workgroup LANs eventually become too difficult to administer and should be replaced with alternative solutions like domains or other client/server approaches.

