SSTK has two methods of segmenting stakeholders:
Contact Groups
Tags
Best practice on SSTK is to have a stakeholder assigned to a contact group, as that is the primary way of segmenting them. A contact group is deemed a FORMAL distribution group.
A stakeholder can belong to several contact groups for example a business owner may also be a local resident or a council member. They will need to communicate differently depending on the contact group.
Tags can be used as a secondary segmentation for Stakeholders - this where you may add a Tag such as Supporter, detractor, VIP or part of mini project etc. This allows users to filter based upon Tags to get a specific sub section of Stakeholders and the Tags can be across all contact groups.
How to use Tags for Interactions, Tasks & Properties
Tags are the ONLY way to segment Interactions, Tasks and Properties. A Tag can be the same as contact group as MAY want to categorise interactions/tasks/Properties the contact group - i.e. particular communities/interest groups etc as you may want to be able to filter on those for reporting.