Masculine nouns are words for male persons and animals. E.g. father, boy, lion are masculine nouns.
Feminine nouns are words for female persons and animals. E.g. mother, girl, lioness are feminine nouns.
Some nouns can be used for both males and females. E.g. doctor, singer, teacher, dentist, scientist
Nouns that are neither masculine nor feminine are called neuter nouns. E.g. bench, waterfall, wind, floor.