Mycorrhiza is a friendship between a fungus and a plant. The fungus is like a little helper for the plant because it can help it get food and water from the soil. The fungus has tiny branches called hyphae that can reach all over the soil and find things that the plant can use to grow.
The plant gives the fungus a place to live inside its roots so it can get some of the food the plant makes from sunlight. The plant also gives the fungus some sugar that it makes from photosynthesis, which is like cooking for your friend who helps you.
Together, the plant and the fungus are really strong and can help each other grow bigger and healthier!