Online fraud can come in the form of e-mail scams, special offers that seem too good to be true (because they are), viruses and spyware.
Any fraud that takes place electronically through your computer is considered online fraud.
The goal of these activities is to gain access to your personal information for criminal activity. Solicitations that may seem innocent, including those that seem to come from institutions you have relationships with, can in fact be fraudulent.
The key is to look for inappropriate requests for personal information, including account numbers, passwords, PIN numbers, social security numbers, etc. Any or all of these may signal an attempt to commit fraud.