What's the meanning of the options of linux command `uname`?

Question

From man uname:

   -a, --all
          print all information [...]
   -m, --machine
          print the machine hardware name
   -p, --processor
          print the processor type or "unknown"
   -i, --hardware-platform
          print the hardware platform or "unknown"

in my computer:

[liwm29@VM-12-11-centos bc_sns]$ uname -p
x86_64
[liwm29@VM-12-11-centos bc_sns]$ uname -m
x86_64
[liwm29@VM-12-11-centos bc_sns]$ uname -i
x86_64

I don't know the difference between them