Redshift is an open-source screen color temperature adjustment tool that automatically adjusts the screen's color temperature based on the time to reduce blue light stimulation and help protect vision. It works by automatically adjusting the screen's color temperature according to the geographical location and time, providing a natural white color during the day and a warmer tone at night. Redshift can be easily installed on Ubuntu using the command 'sudo apt-get install redshift' and can be run either through command line or a configuration file to customize settings such as latitude, longitude, and temperature transitions. It is an eye-protection tool that effectively helps users safeguard their vision by reducing blue light exposure.