Spyware
Spyware is a general term used for programs that covertly monitor your activity on your computer, collecting personal information such as usernames, passwords, account numbers, files and even driver's license or social security numbers. Some spyware focuses on monitoring a person's Internet behavior; This type of spyware often traces the places you visit and the things you do on the web, the emails you write and receive as well as your instant messaging (IM) conversations. After collecting this information, spyware transmits that information to another computer, usually for advertising purposes.
Software that monitors your computer and reveals information collected from an interested party. This can be benign when you keep track of the web pages you visit; Or it can be incredibly invasive when you monitor everything you do with the mouse and keyboard.
Trojan Horse
Software that you thought was going to be a thing, but turns out to be something bad. Named for the legendary "Trojan horse" that seemed to be a gift, but in fact carried a dangerous charge. A Trojan horse is full of tricks as much as the mythological Trojan horse that was named after. The Trojan horse, at first glance it will seem to be a useful software but will really damage once installed or will run on your computer. Those at the receiving end of a Trojan horse are often tricked into opening them because they appear to be receiving legitimate software or files from a legitimate source.
When a Trojan is activated on your computer, results may vary. Some Trojans are designed to be more annoying than malicious (such as changing the desktop, adding silly active desktop icons) or they can cause serious damage by deleting files and destroying information on your system. It is also known that Trojans create a backdoor on your computer that gives malicious users access to your system, possibly allowing confidential or personal information to be compromised. Unlike viruses and worms, Trojans do not reproduce by infecting other files or by self-replicating.