When creating a contact group, there are 2 types of contact groups:

- a static contact group
and
- a dynamic contact group

Static contact groups consist of individual contacts assigned to these groups.
This should be seen as a list of contacts that is manually imported (contact by contact, using an imported file, registration forms, web, ..).

Dynamic contact groups however are a bit different.
When you create a dynamic contact group, you create rules to select contacts.
Each time you use a dynamic contact group, contacts are selected based on those rules.

The benefit of dynamic lists —> you can create a list of prospects that is tailored to specific criteria. If prospect match those criteria, they are added to the dynamic list.
If for some reason they no longer match the criteria, they will be removed from the list.