The Photoshop files are the masters. The png and jpg are copies.
There are two versions plus the favicon and a Bootstrap variant. All versions of the logo are available in various sizes. The Bootstrap versions are used on the web site and have file names *Lg.png, *Md.png, *Sm.png and Xs.png.
The upload process causes image aberration. Therefore; the images are stored as documents and you should always use the original image and not one scaled by the website.