Vectors are a method of describing graphic elements using a mathematical relationship (magnitude and direction) between points.
Programs such as Freehand and Illustrator allow the user to create graphic elements by this method

Viral marketing is a method of promotion that involves the dissemination of messages from person-to-person without the involvement of the originator.
This is commonly achieved through the use of email, but web-based postcards and ‘recommend this site to a friend’ links are other means to the same end.
Viral marketing campaigns generally rely on the strength of the original proposition: be it a product, service or (increasingly) entertainment value.

A virus is a program installed on your computer without your knowledge and typically with malicious intent. The biological description is in reference to the program's ability to replicate and transmit itself to other computers.

A virus may be the cause of you computer restarting unexpectedly, lacking of system memory or the being unable to run applications