DHL Global Mail is more like UPS or USPS?

Can anyone tell me the true functions of DHL Global Mail? I know they provide domestic and international shipments, but I am uncertain what their bread and butter clients would be? Are they more similar to UPS/Fedex where they can pretty much do anything, any size? or more like USPS where its a cheaper solution for light weight products? Anyone that can provide me with a greater understanding of the busines model, would be greatly appreciated.