Windows 7 Installed Windows 7 - what is the second ISO file for?

[wolfv]

I purchased Windows 7 professional and downloaded two ISO files:

en_windows_7_professional_with_sp1_x64_dvd_u_676939.iso
en_windows_7_professional_with_sp1_x86_dvd_u_677056.iso​

I copied the first ISO file to a USB stick and then successfully installed Windows 7 from the USB stick.
I never used the second ISO file. What is the second ISO file for?

Thank you.

 

[Joe S]

The top one is 64 bit x64 and the lower one is 32 bit x86.
Joe

 

[wolfv]

Thanks Joe.