This article explains what a GITIGNORE file is, how it is used, and how to open it on your computer.
Git Tutorial 8 – .gitignore file
A file with the GITIGNORE file extension is a Git Ignore file used with the Git version/source control system.
This file specifies which files and directories to ignore in a given source code. It can be used on a per-path basis, so that the rules are only applied to specific directories, or you can create a global GITIGNORE file that applies to every Git repository you have.
GitHub's .gitignore templates page provides dozens of sample GITIGNORE files recommended for use in various scenarios.