Lists allow to identify OPT-IN contacts or contacts who have given their explicit consent to receive an email. Splio allows to get many lists in order to organize contacts and create a high level targeting (by website, by product, by customer's program etc.).
Filters are rules designed to target contacts with deeper criteria (contacts activity, custom fields etc.). Filters are dynamics and targeted populations can be updated when a campaign is launched if a calculation option is activated. Contacts who have not opted-into any lists will not be included in any filters.