What is a validation pattern?

Answer 1

Usually this refers to a text pattern we can use to validate if the data that a user entered through a web form is correct.

No one would say that an email address without the '@' symbol is correct.

No one would say that a person's name can be composed solely by numbers, e.g.: 12345678

There are some text patterns we can use to prevent an unaware or even malicious user from introducing invalid data in web forms.

Probably all modern high-level programming languages have built in pattern management functions or objects, although I have only used the ones from .NET, PHP and JAVA, apart from POSIX commands (the worst ones, although sometimes simpler to use).

You can take a look at your favourite high-level programming language documentation to get more information about patterns.