The Odin Flash Tool version in this post is made to work for your Android device running Android 5.1.1 Lollipop. You can flash new firmware, custom kernels, gain rooting rights over your operating system and flash a custom recovery if you want to get away from the stock recovery.
Many people prefer buying Samsung devices since they come with the ability to flash with Odin — a flash tool that is easy to use. All you need to do is connect your Samsung device to the computer in download mode, extract the file you are looking to flash and then upload it in the Odin user-interface. These files you are flashing with the Odin app on the computer are usually in the .tar and .tar.md5 formats.
The Odin Downloader comes in several versions. There is no changelog available for either version since this Odin Downloader was not officially released by the Samsung developers; however, a general rule of thumb is the older version work best for the older Android operating systems and the newer versions of Odin are more compatible with the latest Android software updates.
The Odin 3.09 in this post is one of the newer version of the Odin Downloader and is the most popular version installed on Windows computers to this day.