Demonstrations of Wildcards

$ ls
apple.txt  applebad.txt  applegood.txt bag.dat basket.txt
fin.dat    go.exe        tar.tar       zoo.zoo   zz.txt
$ ls *.txt
apple.txt  applebad.txt  applegood.txt basket.txt zz.txt
$ ls a*.txt
apple.txt  applebad.txt  applegood.txt 
$ ls ???.???
bag.dat    fin.dat       tar.tar       zoo.zoo   
$ ls apple[b,g]*.txt
applebad.txt   applegood.txt 
$ ls [a-z]*.txt
apple.txt  applebad.txt  applegood.txt basket.txt zz.txt
$