In SharePoint, if you want to enumerate all the users in the Farm Administrators group, you can use the following script.

 [void][System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SharePoint") 
#Provide the URL of SharePoint Central Administration 
$caURL = "http://sp2010:1000"
$CentralAdmin = new-Object Microsoft.SharePoint.SPSite($caURL) 
$RootWeb = $centralAdmin.RootWeb

#Get all the Group Users... in our case it is "Farm Administrators"
$GroupUsers = $RootWeb.SiteGroups["Farm Administrators"] 

clear
 
foreach ($User in $GroupUsers.Users)
{
    $User.LoginName
}
 
$RootWeb.Dispose()
$CentralAdmin.Dispose() 

As a matter of fact, you can change the URL to any Web Application and get any Group information using the code above.

Hope this helps,
Rahul