SharePoint External Sharing Explained

What are the external sharing features of SharePoint ?

• The ability to share sites and documents with authenticated users. 

    Authenticated users are those who are invited to sign in by using a Microsoft account or Office 365 user ID. 

• The ability to share sites and documents with guest users. 

    Guest users, also called anonymous users, don’t need a Microsoft account or Office 365 user ID to access your sites and documents. They access via guest links that you or your employees give to them.

• The ability to turn external sharing on or off globally for an entire SharePoint Online environment (or tenant). 

   Turning external sharing off at the tenant level means no documents, sites, or site collections can be shared externally.

• The ability to turn external sharing on or off for individual site collections. 

   This provides you with the ability to secure content on specific site collections that you do not want to be shared. 

Reference: 

http://office.microsoft.com/en-us/office365-sharepoint-online-enterprise-help/manage-external-sharing-for-your-sharepoint-online-environment-HA102849864.aspx

Share sites or documents with people outside your organization.

There are three ways that you can do this:

• You can share an entire site by inviting external users to sign in to your site using a Microsoft account or Office 365 user ID.

• You can share individual documents by inviting external users to sign in to your site using a Microsoft account or Office 365 user ID.

• You can post or send users a guest link that they can use to view individual documents on your site anonymously.

Reference:

http://office.microsoft.com/en-us/office365-sharepoint-online-enterprise-help/share-sites-or-documents-with-people-outside-your-organization-HA102894713.aspx?CTT=5&origin=HA102849864