Recursive `make` and `-j`

The article explains how to use the `-j` option in `make` to speed up the build process by making it recursive. The author describes the default behavior of `make` as non-recursive, which can lead to slow builds due to the sequential execution of targets. The `-j` option allows for concurrent execution of targets, significantly reducing build times. The author provides examples and code snippets to demonstrate the use of `-j` with `make` and its benefits.