Aerifying is very similar to what the name sounds like, bring air back into the grass.
Aerification is the process of
either poking holes with solid tines or removing small cores of soil from the field using hollow tines to reduce soil compaction and promote root growth for healthier turfgrass. By taking out small cores of soil about 2-3 inches deep it allows for the oxygen in the air to reach the roots of the already existing turfgrass. The increase in oxygen not only helps root growth, but also its overall strength. This is especially important when the area being aerated is a sports field that takes a great deal of foot traffic.
Soil compaction can be extremely detrimental to sports fields and can actually cause the leaf part of the grass to die off. A compacted soil also cannot hold large amounts of water, as it becomes not porous enough to allow water to pass through. Aerifying a field or lawn will help alleviate the issues that soil compaction brings and help with grass growth.