If your are learning to code to Arduino and you write your own sketchs sooner to later you will need to learn about avrdude, so let's do that.
avrdude is a command line utility developed by Atmel.
It is used to burn sketches to your Arduino, configure your Arduino register and fuses and also flash a different bootloader then the stock one for example the optiboot a smaller bootloader which will free up some memory space for your sketch.
This command will burn your Arduino with custom bootloader hex file.
Check out this article about this custom bootloader to learn more.
You can learn how to install it here.
if you are not familiar with adafruit you should definitely do so.
This site by ladyada explains everything you should know about avrdude commands.