Odin Samsung Flasher Download
Download Odin Latest v3.09
Download Odin v3.09 Free
Most of the ROMs you are going to flash with Odin are the official stock Samsung ROMs (or leaked stock ROMs). Custom ROMs are rerely flashable by Odin because they come with .zip extension that Odin does not recognize (it recognizes .tar files).
Custom kernels, however, are sometimes provided in .tar format by their developers (e.g. CF-Root kernels), so that they can be flashed by Odin.When your phone is new and running official firmware you most often cannot flash a custom ROM to it because a Samsung phone often requires a custom recovery and root rights that are included in a custom kernel to be able to flash custom ROMs. That's why Odin often comes in handy in rooting and flashing a custom firmware to your phone because you (often) can flash a custom kernel with it that already includes root and custom recovery and enables you to flash custom firmware (custom ROMs). I use the word "often" very frequently in the previous sentence because every Samsung smartphone is different and requires various procedures for rooting it and flashing custom ROMs