A group is a customizable database of contacts that can be private or shared.
You can create as many groups as you want, directly from the sidebar. Usually, users tend to create groups for every type of contact they need to manage: a list of investors, influencers, candidates, suppliers etc.
Groups can be private or shared. You can control who has access by using the 'Share group' button.
Then your shared group will appear under the section "Groups" and the private ones, under the section "Private groups" in the left sidebar.
Here is a quick video on 'How to share groups on folk' 🎥