Regular expressions are a way to make your bot listen intelligently for what you'd like to respond to. Regular expressions are utilized by listeners, even if they are created the "basic" way. Let's take a closer look at how to use regular expressions.
You may have hovered over the question mark when creating listeners, if so, you will have seen this information. It's a good intro to basic usage. Here are some of the most basic and useful regular expressions and examples:
| - separates lists of words to be matched ("cat|dog" will match a phrase containing either "cat" or "dog")
^ - match the start of a user's input ("^cat" will match anything starting with "cat")
$ - match the very end of a user's input ("cat$" will match any sentence ending with "cat")
\b - match a word break ("\bcat\b" will match "cat" exactly, but not "cats" or "vacation")
\s\ - a literal space between words ("cat\s\and\s\dog")
(?=.*\bcat\b)(?=.*\bdog\b).* listens for a phrase containing two words (will match any phrase with the words "cat" and "dog" somewhere in it)