The opening of yarn is a process that separates compressed fibers into small tufts using a bale opener. Here's some more information about the opening process:
Principle
The bale opener uses sets of teeth to hold the fiber tufts and drag them across another set of teeth.
Goal
The goal is to separate the fibers into small tufts with minimal lint loss.
Benefits
The opening process helps remove unwanted foreign particles from the fibers, which results in higher quality cotton fibers.