When you follow a coworker in Workplace, you'll see their posts in your News Feed. You can follow coworkers, people on other teams, or executives in your company. You'll only see posts that are visible to the entire company or posted to groups you're a member of.
When a coworker follows you, they'll see your posts that are visible to your company in their News Feed. If you post to a closed or secret group, your coworkers will only see it if they're members of the group.
When you unfollow a coworker, you'll see fewer posts from them in your News Feed. You can reconnect with the coworker that you unfollowed by following them again.