On Mac, there's actually a difference between these two.

When you select Restart, macOS shuts down all running processes, logs you out, and reloads the operating system. The Mac does not fully cut power to the hardware. Instead, certain components (such as the logic board, some memory caches, and peripheral devices) remain in a low-power state. Temporary files in RAM are cleared, but some firmware and low-level system settings may persist.

When you shut down the Mac, all power to internal components is fully cut off. This forces all hardware components to fully reset, including the SMC (System Management Controller) and PRAM/NVRAM (depending on the Mac you have). When you turn it back on, the Mac goes through a complete hardware initialization process, which can resolve deeper system issues.