There are two main structures of fungi: sepatate and aseptate. Septate fungi are more advanced and separated into smaller sections by a septum membrane. Aseptate fungi are more primitive and do not contain septum or separate sections.
Fungi can take many different shapes and sizes but they normally follow this basic structure. Hyphae are individual thread-like filaments that intertwine to form a web-like structure called a mycelium.
Certain hyphae can produce reproductive spores by budding off at the ends. That is how fungi can travel through the air and find their way to many different surfaces.
Most hyphae are 2-10 micrometers across but some are nearly 300 micrometers across. Just to give you an idea of the size of a micrometer, a human hair is about 100 micrometers across. This means that a person can't see hyphae with the naked eye.
Athlete's Foot (tinea pedis) is caused by a fungus. It can occur in individuals whose feet are damp or sweaty. It affects the soles of the feet and areas between the toes. Swimming pools, locker rooms, and showers are easy places to get athletes foot because they provide damp environments where people walk around barefoot. The hyphae of tinea pedis dig into the skin (normally between the toes) where they get their nutrients.