There are many different ways to grow cannabis and the growth medium used is the substance or technique applied (this can be anything from soil to perilites). The medium is what makes sure the plant roots are getting the water, oxygen and nutrients it needs to thrive - it also plays a significant factor in the final harvested product.
Soil is the most natural, simplest and intuitive way to grow.
Simple with more margin for error
Great for outdoor
More susceptible to pests
Technically, any growing medium besides soil is considered hydroponics (including growing in a soilless medium like coco coir). It is a type of horticulture that relies on water to deliver oxygen and nutrients to the plant.
Roots in misted air.
Aeroponic systems grow plants suspended in air, supplying the roots with nutrients and water through a mist.
Fish feed the roots.
The difference between hydroponics and aquaponics is that aquaponic systems are also home to fish.
Deep Water Culture
This method has many different variations however the roots grow in a nutrient reservoir that is oxygenated by bubbling air through water.
Less likely to get pests
Set up costs are higher
Nutrient formula must be very dialled in
Tough to do outdoors