Characterization

The Kingdom Fungi contains very important organism. They breakdown dead organic material, and they continue the cycle of nutrients("Microbiology"). Moreover, most vascular plants need symbiotic fungi to be able to grow, or mycorrhizae, that inhabit their roots and supply essential nutrients. Other fungi provide numerous drugs (such as penicillin and other antibiotics), foods like mushrooms, truffles and morels, and the bubbles in bread, champagne, and beer. Fungi also cause plants diseases, and they may cause grave problems to crops.
The Kingdom Fungi is very resistant to changes in the environment ("Microbiology"). They can survive environmental conditions that would put other eukaryote life-forms under a lot of stress. This happens because of their method of propagation, known as the spore.  
Fungi are unable to produce their own food. They obtain their food from dead organic matter, or from living organisms. The source of their food is called a substrate if it is dead and a host if it is living.

The body, called mycelium, of fungi is made of threads called hyphae. These threads absorb nutrients from the substrate in order to grow and produce fruiting bodies. These bodies are the visible parts of the fungus ("Facts").

Mycorrhizae are a symbiotic process between a fungus hyphae and a living plant root. When a fungus is absorbing nutrients from dead organisms, it is called a decomposer and not symbiotic.

There are three types of symbiosis:
Parasitic: benefits the fungus but harms the host.
Mutual: both fungus and host benefit from their partnership.
Neutral: benefits the fungus with no harm or benefit to the host.

Mycorrhizal symbioses are mutual and two types are known: ectomycorrhizae and endomycorrhizae ("Facts").

In ectomycorrhizal symbiosis, the hyphae gets inbetween the root. Some threads spread from the root into the soil to absorb minerals. Others spread into the root, between root cells. These hyphae connect the tree with the soil’s minerals, but in exchange get carbohydrates produced by the tree's photosynthesis. This type of symbioses creates a close physical relationship.

Endomycorrhizal fungi do not reach the root. Hyphae enter into the root cells("Facts").


Reference:
"Fun Facts about Fungi". online: http://www.herb.lsa.umich.edu/kidpage/Mycorhiz.htm
"Microbiology: Fungi" online: http://www.theguardians.com/Microbiology/gm_mbf08.htm