A Gemfile is a file used in Ruby programming to manage dependencies for a project. It specifies which Ruby libraries, known as gems, are required for the application to run. By listing these gems, developers can ensure that everyone working on the project uses the same versions, which helps maintain consistency and avoid conflicts.
To install the gems listed in a Gemfile, developers use the command `bundle install`, which is part of the Bundler tool. This tool simplifies the process of managing gem dependencies, making it easier to develop and deploy Ruby applications while ensuring that all necessary libraries are available.