Trojan is a Trojan. Worms are programs that replicate themselves from system to system without the use of a host file. This is in contrast to viruses, which requires the spreading of an infected host file. Although worms generally exist inside of other files, often Word or Excel documents, there is a difference between how worms and viruses use the host file. The entire document will travel from computer to computer, so the entire document should be considered the worm.
Worm is a particularly prevalent example.
Virus hoaxes are messages, almost always sent by email, that amount to little more than chain letters. Most virus hoax warnings do not deviate far from this pattern. Because of the publicity that viruses have received, it is easy to blame any computer problem on a virus. There are no viruses that can physically damage computer hardware, such as chips, boards, and monitors. The computer beeps at startup with no screen display.