Are you wondering about the difference between the x86 and the x64? One main difference is the bit of each operating system. When you say x86, this would refer to the 32 bit CPU while the x64 will refer to the 64 bit CPU and the overall operating system.
Take note that the 32 bit CPU is not meant to handle a lot of memory which means that you can choose this if you know that you do not need the memory too much.
If you would choose the x64, you can expect that this will run in both 32 bit and 64-bit programs which can make this the better option between the two. This is especially helpful when you are looking for something that is more modern.