Tagging can be useful when you need something to quickly filter Contacts by. For example, if certain Contacts are more valuable than others, adding a “Premium” Tag to them can help differentiate them from other Contacts. You can then select this Tag from your filter options on the right side of the Contacts page in order to see only those which have been tagged with it. This can be a great way to categorize and group various people in your Contact list. Tags can also be used to categorize both Deals and Leads.
Tags can also be used to filter your Reports. Simply select the Report that you'd like to see, then select the relevant Tag from the top of the page. This will filter the Report to only display information from items with that Tag.
Using Custom Fields
Custom Fields can also be used as filtering options, but their real use comes when you need to store information that isn’t provided by Base’s default set of fields. For example, you can add a Skype name or an anniversary date to a Contact using Custom Fields. These are things that you might not necessarily want to filter by, but are still great to have on a contact card for reference.