Logs
A log is the simplest kind of note: a line of text your app writes down as something happens — "user signed in", "payment failed: card declined", "cache rebuilt in 1.2s". If you have ever added a println to work out what your program was doing, you have written a log.
Logs are the running diary of your app. When something goes wrong on a real person's device, the logs are usually the first place you look.
Record a log
Each line finishes the moment it is written to the device — the same as traces and metrics — and is delivered later with no duplicates. That whole journey is on Device to dashboard.
Starting over with a clean slate
You can throw away everything recorded so far — logs included — while the app is still running, with no restart and nothing to delete by hand. Logs are forgotten in a way other devices respect, so one you sync with later cannot hand them back. That is on Device to dashboard, because the same call clears all three kinds of note at once.
Logs you already write
Your app almost certainly writes logs already, through a logging library. You do not have to rewrite any of that to get those lines into the same offline-safe buffer — and you can then reach into a device you cannot otherwise get to (a tester's phone, a CI simulator) and pull the logs off from a test. That is its own short how-to: Capturing.