On IFTTT, there are two types of Applets, polling Applets and realtime Applets. Polling Applets use polling triggers, while realtime Applets use realtime triggers.
Polling Applets
Polling Applets run after IFTTT reaches out to the trigger service and finds a new trigger event. These trigger checks occur every 5 minutes for Pro and Pro+ users, and every hour for Free users.
An example of a polling trigger is Twitter - New tweet by a specific user:
Because of the reactive nature of polling triggers, we expect polling Applets to run within 5 minutes of a trigger event occurring for Pro and Pro+ users, and within one hour for Free users.
Realtime Applets
Realtime Applets run after the trigger service notifies IFTTT of a new trigger event. Since IFTTT is notified proactively of new trigger events, realtime Applets normally run within a few seconds of a trigger event occurring.
An example of a realtime trigger is Button widget - Button press:
