GitHub - MarlinFirmware/Marlin: Marlin is an optimized firmware for RepRap 3D printers based on the Arduino platform. Many commercial 3D printers come with Marlin installed. Check with your vendor if you need
What is Marlin? | Marlin Firmware
How To Successfully Flash Your 3D Printer's Firmware | MatterHackers
Build a 3D printer - Part 13: Software | ezContents blog
Step by Step guide to setting up Marlin for Auto Bed Leveling