The fungus in mouth is called Candida, which is yeast-like. Normally people have Candida in mouth, throat and esophagus, Candida lives with other bacteria in your body and is managed under control and in balance. Sometimes the balance is interrupted, Candida over grows, cause the disease called Candidasis.
In mouth it looks like white sticky patch.
People who have weak immune, or diabetes, may have recurring Candidasis a lot.