In computer terms, worms are really a subset of viruses, but they have the ability to replicate by themselves, they do not require a host file.
A virus is a program which replicate by copying itself, either exactly, or in a modified form, into another piece of executable code.
A Trojan Horse, often referred to as just a Trojan, is a program which purports to do one thing, but actually does another.
The term Spyware has been used in two ways. In its narrow sense, Spyware is a term for Tracking Software deployed without adequate notice, consent, or control for the user.
Scams are very similar to phishing, but are not usually interested in obtaining your details, they often appeal to a sense of compassion or to human greed.
A rootkit is a collection of one or more tools designed to covertly maintain control of a computer.
Phishing (pronounced in the same way as fishing) is a social engineering attack which attempts to fraudulently acquire sensitive personal information, such as passwords and/or credit card details.
The additional functionality, for instance data stealing, file deletion, disk overwriting, BIOS flashing etc that may be included in a virus worm or Trojan Horse.
Malware stands for MALicious SoftWARE. Terms such as Virus, Trojan, Worm, and Bot all have specific meanings.
Hoaxes are usually silly pranks, and are a form of chain mail, and are often also Urban Legends.
A botnet is a group of bot infected PCs that are all controlled by the same "command and control centre".
Short for "Robot" a bot is a program that is designed to automate tasks.
A type of Advertising Display Software, specifically certain executable applications whose primary purpose is to deliver advertising content potentially in a manner or context that may be unexpected and unwanted by users.