All Russian nouns belong to one of three grammatical genders: masculine, neuter or feminine. Do not confuse gender with sex; the word for table in Russian is a masculine gender noun, but there's nothing male about the object; book in Russian is a feminine gender noun, but there's nothing inherently female about it. However, nouns referring to male beings will (usually) be masculine gender; those referring to female beings will be feminine gender.
In most cases, the gender of the noun can be determined by its ending. The table below illustrates this:
MASCULINE | NEUTER | FEMININE |
end in a consonant or-b | end in -о or -е | end in -а, -я or -ь |
паспорт автомобиль портфель | озеро море пальто | виза фамилия Сибирь |
он | оно | она |