Binwalk is a device for looking a given binary image for embedded documents and executable code. Its far designed for figuring out files and code embedded inner of firmware images. Binwalk uses the libmagic library, so it is compatible with magic signatures created for the Unix file utility. It additionally consists of a custom magic signature report which contains progressed signatures for documents which are typically found in firmware photos including compressed/archived files, firmware headers, Linux kernels, bootloaders, and so forth.”]
Source: https://gbhackers.com/analyzing-embedded-files-and-executable-code-with-frimware-images-binwalk/