Embedded debugging is the work of finding and fixing bugs in software that runs on a microcontroller or other small device rather than on a regular computer. It is harder than debugging an ordinary program because the target is constrained in ways a desktop is not: little memory, no screen or keyboard, often no operating system, and frequently strict timing requirements where a delay introduced by debugging can itself change the behavior being investigated.
The simplest technique is printf-over-UART: the program sends short text messages out a serial port, which the developer watches on a host computer to trace what the code is doing. It is easy to set up and works almost anywhere, but it is intrusive. Each message takes time and memory, and on a system with tight timing the act of printing can mask or even cause the very problem under study. It also gives no way to pause the program and inspect its state.
For deeper insight, developers use in-circuit debuggers that connect to the chip through a hardware interface such as JTAG or SWD. These let a tool on the host halt the processor, set breakpoints, single-step through instructions, and read or change registers and memory directly on the running target. A common open-source setup pairs OpenOCD, which speaks to the JTAG or SWD adapter, with GDB, the GNU debugger. The OpenOCD documentation describes how it exposes the target to GDB over a remote-debugging connection, so a developer uses familiar GDB commands while OpenOCD handles the low-level communication with the chip.
Some problems are about timing and signals rather than program logic, and for those a logic analyzer or oscilloscope is the right tool. By capturing the actual electrical activity on the pins and buses, these instruments reveal whether two devices are communicating correctly, whether an interrupt fired when expected, or whether a signal is glitching, none of which a software debugger can see.
Embedded debugging matters because so much of the world now runs on these small devices, from appliances to vehicles to industrial controls, where a bug can be expensive or dangerous and is often hard to reproduce. The combination of on-target hardware debuggers, careful logging, and signal-level instruments is what makes it possible to understand and trust software running on hardware you cannot simply attach a normal debugger to.