WP Sync is a bridge engine. Once you understand four words, every screen in the plugin makes sense.
Source:
Any connection WP Sync can read new contacts from. That might be an autoresponder list, a WordPress form, an inbound webhook, a Google Sheet, a webinar, a WooCommerce order, a Stripe or PayPal payment, a Calendly booking, a Facebook lead form, a course enrollment or a WarriorPlus sale.
Destination:
Any connection WP Sync writes contacts to. That might be another autoresponder list, a spreadsheet row, a webinar registration, an outbound webhook, a Slack, Discord or Telegram message, a help desk contact or a CRM record.
Bridge:
The rule that links one source to one or more destinations. Each destination on the bridge carries its own field mapping, its own action and its own optional delay. Bridges can be paused, cloned, tested and reordered.
How new is detected:
Some connections are push. The other app posts the event to your site the instant it happens, so there is nothing to wait for. Other connections are polled. A WordPress cron job runs every five minutes, asks the app what is new since the last successful check, and relays anything it finds. One more idea worth knowing early: a bridge does not need a source at all. Choosing No source creates an action you trigger yourself, for example from a tracking link click or a conversion, where the trigger is what fires the bridge and no source list is required.