There are two complementary ways to target the right people.
Lists are groups you add contacts to explicitly — for example "Newsletter subscribers" or "Trade-show leads." A contact stays on a list until you remove them. Lists are what you point a campaign, sequence, or broadcast at.
Filters select contacts by their attributes — status, lifecycle stage, country, owner, tags, and even social follower counts. Because filters read live from your database, the results always reflect your current contacts.
Use a list when you want a stable, hand-picked group; use filters when you want everyone matching a live condition (for example, all active contacts in a country). You can build a targeted audience with filters and act on it directly.