Interacting with the file system is a crucial aspect of command-line interface (CLI) applications, particularly when it comes to recursively traversing directories and analyzing files. Go simplifies this process through the `walk` function in the `filepath` package, which allows developers to start at a root directory and execute a given function at each file or directory node within the tree structure. This lesson demonstrates how to create an application called `walker`, which collects statistics such as the total number of files, directories, and the cumulative size of the files within a specified directory. The application also includes functionality to filter files by their extensions and showcases the versatility of the `io/fs` package for further enhancements. Overall, understanding these tools enables developers to effectively manage and manipulate file systems in their Go applications.