A Flow is an automation: Automated sequences that send emails and SMS messages triggered by customer behavior. Instead of you picking recipients and a date, a flow starts automatically for each customer when a chosen event happens (for example New Registered User, Order: Create, Order: Abandoned Cart, Subscription: Pause, User: Birthday, User: New Newsletter) and then runs a chain of blocks you design: Email, SMS, Time Delay, Conditional (branch on opened/clicked/delivered/replied) and List Action.

Use a campaign for one-off broadcasts (this week's menu, a promotion). Use a flow for evergreen messages that should reach each customer at the right moment (welcome series, abandoned-cart reminder, win-back after a cancellation, birthday greeting). Flows run only while switched ON and only for events that happen after they are turned on.