Mycorrhizae is a beneficial bacteria made up of tiny fungal filaments that attach themselves to roots and spread out into the media and gather nutrients and moisture for the plant, which in turn provides the bacteria with sugars passed down to its roots. The term mycorrhiza can refer to both the role of the fungi in the plants' root system breaking down nutrients to become more readily available for your plant as well as the bacteria itself. Mycorrhiza bacteria is typically more common in soil and soilless media where it tends to create fungal colonies better than in hydroponic environments but there are some mycorrhizae specially made for hydroponics.