Breadcrumbs are an extension of the Track Log capability but operate independently to display a thin green line indicating your aircraft’s path since takeoff. When switched ON in Maps > Settings, the Breadcrumbs trail automatically activates on takeoff and ends when you slow below 40 knots or descend below 250' AGL. Breadcrumbs can be set in More > Settings to persist for as few as 15 minutes up to 4 hours after landing so you can review the path after your flight.
Image 1. Breadcrumbs Shown on the Maps page
Tap a Breadcrumb trail anytime to view flight metrics, to save the Breadcrumb trail as a new Track Log, or to reset it without saving. Saving a Breadcrumb trail as a new track does not affect an ongoing Track Log recording. This means you can use Breadcrumbs to track individual maneuvers by saving a Track Log of each one, then resetting the Breadcrumbs after saving. At the conclusion of the flight, you will have the entire flight Track Log as well as any individual Track Logs you saved from Breadcrumbs.
Here's a video that shows the Breadcrumb feature in action:
Video 1. ForeFlight Quick Tip: Breadcrumbs