5.5
Collisions and Collision Domains in Shared Layer Environments
5.5.4 Collisions as natural functions of shared media environments and collision domains
Normally, people think that collisions are bad because they decrease network performance. However, a certain amount of collisions are a natural function of a shared media environment (i.e. collision domain). This is because large numbers of computers are all trying to communicate with each other at the same time, by using the same wire. 

The history of how Ethernet handles collisions and collision domain dates back to research at the University of Hawaii. In its attempts to develop a wireless communication system for the Islands of Hawaii, university researchers developed a protocol called Aloha. This protocol was instrumental in the development of Ethernet.