just run echo * in your directory. That's the same argument grep will get(instead of the * ) when you pass it * .

grep will run through all those files, if any, and recurse through all the directories, if any. grep recursing down a directory will process all the files/subdirs in that directory. (which includes . files).

If the shell can't expand the * , grep will receive a literal * and try to open a file/directory named * .