External users in workgroups (Extranet)

Extranet users are being invited to the particular Extranet workgroup & have access to the group tools -  group Messages, Drive, Tasks, Calendar, Chat, etc. 

Outside the Extranet workgroup Extranet users also have access to contacts & employees who are listed as Extranet group members:

The Instant Messenger will show Extranet workgroup members & Extranet workgroup chat. This means external user will be able to create person-to-person or private group chats with employees - members of the Extranet group, or use workgroup chat.

See Intranet vs Extranet user comparison chart below:

You can invite external users to your Bitrix24 workgroups only in frames of Extranet Workgroups. Go to Workgroups > Create > External Workgroup or enable option Available on extranet in workgroup settings:

Use invite employees section to add employees. Use Invite external users to add external users to the workgroup:

Extranet workgroups are marked with orange color, so that you can easily understand which groups have external users. You can also add new external users to the existing Extranet workgroup with the help of Actions tab > Invite to Workgroup.

Read more in the article - Move employees to Extranet.