Characterclassese This is the language of character wildcards.

[a-j]  matches any character in the asciicographical range a-j.
[aqm5$] matches any of the characters (list character class)
[a-zA-Z]  matches any alpha character
[0-9]     matches any digit

Magic characters
[
=   indiates a range

Regexese This specifies patterns in text.