The CMYK and VECTOR EPS versions are for PRINTING and are resizable EPS files for commercial or desktop printing.
The PNG versions can be placed on top of images and are RGB with a transparent background. They are also saved as 72dpi files for web use, not intended for commercial printing. A PNG can also be used in place of a JPG format (it serves the same purpose).
The WHITE version is on a PNG transparent background and can be used if the logo is online on top of a confusing or multi-colored background of a partner organization. There is also a vector EPS version if needed for print.