Organization-wide teams are handy for all your company-wide communication needs, because all of your organization's members are automatically added to the organization-wide team. In other words, the organization-wide team's membership is kept in sync with the organization's membership.
So, with organization-wide teams, you can make sure that everyone in your company is included in the necessary conversations — just create them as team conversations. Likewise, should you decide to remove any accounts from your organization, they will also be automatically removed from the organization-wide team and its conversations.
Note that organization-wide teams are a Fleep for Business feature. It is not available for free users of Fleep.