Candida is a genus or grouping of yeasts. Yeasts are a type of fungus. This group of fungi are the most common cause of fungus infections in the world. Most people have or are exposed to this group of fungus but are not sick. If a person is weak because of another illness, this fungus can cause disease. "Candida albicans" is the most common kind of Candida. Infection with this fungus is called candidiasis or thrush. Other species in this group can be found in the human gut.