An extranet is a strategic platform used to interact with specific, external stakeholders. By integrating your Sitecore CMS or Umbraco CMS to underlying systems (e.g. financial management systems, ERP, CRM, etc.) extranet users can practically service themselves, thus bringing service levels up and administrative expenses down.
As well as keeping administrative expenses down to a minimum, an extranet can also establish better relations with your customers, business partners, investors and stakeholders. And because you define which stakeholders have access to the extranet, it can function as an effective tool for targeted communication.