Growing mediums
Cannabis can be grown in many different growing mediums each with differing aeration, water retention, and pH
Mediums
Soil
The traditional growth medium. Easily available, the pH is mostly determined by the water applied, although soil provides a buffer. This is the most simple growth medium, good for beginners. More advanced growers may wish to create a type of organic "living soil" via methods such as Bokashi
Coco Coir
A growth medium made from the fiberous husk of coconuts. It is more suited to hydroponic grows but it can be potted and/or mixed with soil. Coco coir provides less of a pH buffer than soil however this can be overcome by mixing the too. Its also notable that coco coir is inert and provides no nutrients itself, meaning that nutrients must be added via additives.
Coco coir also has excellent water rentention capabilities similar to vermiculite and can hold 10x its weight in water.
Additives
Vermiculite
Has very good water retention properties and provides Silica which has a variety of uses in cannabis[1]
Perlite
Perlite is a derivative of volcanic glass that can be added to soil or coco coir to increase aeration, by keeping the soil less compact. It also holds a lot of moisture. Perlite should be wet before use as it can easily spread dust
Mycorrhizal Fungi
Some fungi can live symbiotically with the plant's root system, they consume some glucose created by the plant while increasing nutrient uptake. Some soil mixes come with myco already added, you can buy it separately and combine with your medium, or it can be added to the medium in the hole where a plant will be transplanted.