Drip campaigns differ from broadcast campaigns in two ways: they are time-relative to each recipient (day 1, day 3, day 7 from the trigger, not a calendar date), and they are written once and run continuously.
Common patterns: a welcome sequence after newsletter sign-up, an onboarding sequence after free-trial activation, a nurture sequence after a content download, a re-engagement sequence triggered by 60 days of inactivity. Each pattern has its own optimal cadence — onboarding wants daily for the first week, nurture wants weekly for a month.
Drips are usually contrasted with 'workflows' (behavioural automations that branch on actions) and 'broadcasts' (one-time campaigns sent to everyone at once). A modern email platform supports all three, and a mature email program uses each for its right job.