About
Because a file system arranges file in a tree structure (file system tree), when you want to read it, you perform a Tree - (Traversal|Search) which is therefore a recursion
Articles Related
Example
Pseudo code
function scanDirectory(directoryPath){
for (childrenPath in directoryPath) {
if (childrenPath is a directory) {
print("A directory was found"+childrenPath);
scanDirectory(childrenPath); // the recursion
} else {
print("A file was found"+childrenPath);
}
}
scanDirectory("."); // Scan the current directory