See also the official documentation:

• Help Center > Members Manual > Viewing the directory
• Help Center > Members Manual > Viewing the member list
• Help Center > Group Owners Manual > Managing members > Reviewing the member list

Directory vs the Members List

There are two places with group member names:

1. one that has all members (the Members List in the Admin area) and
2. the Directory. However, not all members are in the Directory - members have to opt in.

Details:

The Member List is an index of subscriptions. 

Its visibility is set by Admin->Settings->Privacy->Members Visible. 

Content is restricted by the system to designated fields (email address, display name, join date, mail delivery, etc) that are necessary to perform system functions. 

For privacy reasons, the members list will usually be visible only to Owners and Moderators, who can also "click through" each member record to send +owner messages, view activity, save notes about this subscription, or generally manage subscription settings. 

If you as an Owner want members to be able to "see" every other member in the group without forcing everyone to jump through the profile hoop, you must make the member list visible. Doing so will not give Subscribers access to the underlying information, however -- only the "stuff" that appears in the main index (Display Name, Message Delivery, Email Address, and Join Date). This can only be done if you first select the Restricted method of Spam Control.

The Directory is an index of member profiles.

A member's profile will be visible in the Directory only if:

-- the directory is enabled in Admin, Settings, Features
-- they create a profile and choose to share it (Subscription->Group Profile->Edit Group Profile->Profile Privacy*), and,
-- group settings under Privacy->Member Directory is set to Members, OR
-- the person viewing the Directory has Owner/Moderator privileges. 

Accounts that are bouncing (B status badge), or whose email address is not confirmed (NC), also do not appear in the Directory.

Each member "owns" their own profile, and if they choose not to create one (or keep it hidden), that's their prerogative. The content of a member's profile can be anything they choose to put in it. Group Owners and Moderators cannot edit user profiles.

Searching the Members list: filter using the dropdown menu

*Account and group profiles may also be edited via Account->Identity