In A CSMA/CD network, a normal process that occurs when two stations have tried to send data at the same time. When this happens, both stations stop, wait a random interval, and try again. If they still collide, they will wait twice the random amount, continuing to double the amount until the channel is clear and the entire frame is sent.

Many people think collisions are a sign of a sick network but that isn't necessarily true. In modern Ethernets, they can indicate a speed or duplex mismatch, but if you're only seeing occasional collisions, it's just the intrinisic data link layer protocol doing its job. There's always going to be a chance that two stations on a segment or in a collision domain will transmit simultaneously if there is more than one device on the segment, which there always is, even if it's just a switch port and a computer.

this was a nodeshell