Interactions are the emails and calendar events imported when you sync your Gmail accounts to folk.
Most of your interactions will be imported except the following:
More than 3 years old interactions will not be imported
Unread messages will not be imported
Recurring events from Google Calendar will not be imported
Emails with more than 20 recipients will not be imported
Events with more than 20 attendees will not be imported
Emails received from subscriptions and mailing lists won't be imported