Moulds are a form of fungi, as are yeast and mushrooms.
And, depending upon circumstances, the same mould can be either useful or a health hazard. In most non-contaminated workplaces the possible mould exposure would not be expected to present a health hazard except to very susceptible individuals. In contaminated situations the risk from exposure to mould increases. Reactions are varied and complex depending upon many factors. Human factors include personal susceptibility, route of exposure, age and state of health.