define direct effect
Broadly, there are two kinds of networks effects: Direct network effects: An increase in usage leads to a direct increase in value for other users. For example, telephone systems, fax machines, and social networks all imply direct contact among users. A direct network effect is called a same-side network effect. An example is online gamers who benefit from participation of other gamers. Indirect network effects: Increases in usage of one product or network spawn increases in the value of a complementary product or network, which can in turn increase the value of the original.