Wildcard is an unknown or unpredictable factor.

You can also nest brace expansion lists in the mkdir command. For example, in the articles subdirectory under the htg directory, we want to create two subdirectories called new and rewritten. So, we type the following command at the prompt and press Enter. mkdir -p htg/{articles/{new,rewrites},images,notes,done}

If you want rules to apply to an arbitrarily deep hierarchy, use the recursive wildcard syntax, {name=**}