Trojans are malicious applications that pose themselves as legitimate software in order to trick users to install them. Once on the victim's machine, it may run any number of malicious process to steal vital information or inflict damage to other software.
Dloader.C.man drops files without users knowledge. These other files download and install trojans and adware. It has been known to use the WMDM PMSP Service Vulnerability in order to connect to malicious sites.