You can use external groups to collaborate with users from outside your community.
When you create an external group, you can invite users from outside the community to work with community users. These groups usually serve a specific purpose, such as working on a project with a vendor. External contributors can see content only in groups they belong to.
The external contributor brings a fresh perspective and their expertise to an internal or employee community where you would usually suffer the pains of long email threads or time-consuming conference calls to get information from people outside your community. These users can provide quick answers, share files, and collaborate on documents.