Some more open than others. Some with multiple communities inside of one another. Some where the community changes based on the organizations trajectory.
Workplace community is inherently based on teamwork: groups of people working together on a common project, cause or goal. These are typically the things that bring you together in a working environment. Of course, social interactions and friendships that are formed, change and morph these group interactions.
Add some tips for efficient and relationship building teamwork to your toolkit in this article from 99u.
What is your workplace community like?