What is triggering and why is it the key skill?

Triggering is configuring the instrument to start (or center) its capture on a defined event, rather than recording whatever happens to be present when you press the button. Because both scopes and logic analyzers capture a finite time window (limited by memory depth), you have to tell the instrument what moment matters, a rising or falling edge on a channel, a voltage threshold, a specific pattern across several channels, a protocol condition like an I²C START or a particular address or UART byte, or a glitch/runt (a pulse narrower than a valid bit). Single-shot mode arms the trigger once to catch a rare, one-time event, like a fault that occurs every few hours. Triggering is the key skill because the difference between a useful and a useless measurement is whether the capture is centered on the failing event: a well-chosen trigger catches the exact transaction or glitch that's misbehaving, while a poor or default trigger just gives you a screenful of normal, irrelevant activity. For hard-to-catch bugs, a once-in-a-million corrupted frame, an occasional missed deadline, a sporadic glitch, setting up a precise trigger (e.g., protocol condition plus a glitch trigger, in single-shot) is often the entire battle; once you've captured the moment, the analysis is easy. So mastering triggers turns the instrument from "shows me signals" into "shows me the signal at the instant it went wrong."