In the Dialer, a group and a tag are used to categorize and manage contacts or leads efficiently. These options help users keep track of their contacts or leads and facilitate targeted communication and marketing efforts.

Here's a description of each:

A group is a predefined or user-created category or segment into which contacts or leads are grouped based on specific criteria or characteristics. For example, you might create groups for "Customers", "Prospects", "Leads", "Personal Contacts", "Business Contacts", "Vendors", and whatnot.
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Groups are typically used as the primary-level category to organize contacts or leads. They are assigned to campaigns for targeted marketing, communications, and/or outbound activities.

A tag is a customizable label or keyword that can be applied to individual contacts or leads. Tags are more granular than groups and allow you to categorize contacts or leads based on specific attributes.
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Tags are typically used as the secondary-level category to organize contacts or leads. They are used to label contacts or leads based on specific actions, preferences, interests, or custom criteria. For instance, you might tag contacts with "interested", "contacted", "dialer", "booked", "sold", "dnc", and whatnot.

Thus, both groups and tags work together to provide a flexible and organized system for managing contacts or leads — allowing for efficient communication and targeted marketing efforts.