An extension or library used in certain programming languages or frameworks (namely Ruby or Yii2) for generating fake data for debug purposes and testing.
In Ruby, Faker, a port of Data::Faker from Perl, is used to easily generate fake data: names, addresses, phone numbers, etc.
In Yii2, Faker can generate random strings (like name, address, phone number or anything), random numbers, keys or harshes as well as long sentences of fake text. It can be accessed in OOP style.
A PHP library is available for Faker that is used in some frameworks such as Laravel.