foo.ps1

# get all of the groups under a provided organizational unit (recursive)
$groups = Get-ADGroup -Filter * -SearchBase '<distinguishedName>' -Properties Description

# loop through all the groups we just got
foreach ($group in $groups) {
    # get the members of the group, and loop through those members
    Get-ADGroupMember -Identity $group | foreach {
        # create a pscustomobject to store our data
        [pscustomobject]@{
            groupname           = $group.Name
            groupdescription    = $group.Description
            samaccountname      = $_.samAccountName
            displayname         = $_.displayName
            lastlogondate       = $_.lastLogonDate
            enabled             = $_.enabled
        } | # pipeline this new object to our csv and append it
        Export-Csv -Path "C:\Temp\Security Groups.csv" -Append -NoTypeInformation
    }
}