Hard and Soft Consonants. The consonants may be hard of soft depending on what letters follow them.
The vowels а, о, у, ы, э indicate that a preceeding consonant is hard.
The vowels я, ё, ю, и, е indicate the softness of a preceeding consonant.
For example,
ба – бя
бу – бю
In the first case the letter б is hard, in the second one it is soft.
The letter ь has no sound but indicates the softness of a preceeding consonant:
стол – соль (table – salt)
Listen to the next words to see the difference between soft and hard consonants:
река – рука (river – arm)
луна – король (moon – king)
меч – мост (sword – bridge)
паук – пикник (spider – picnic)
Russian words have hard and soft stems. Hard stems end in a hard consonant. In this case the ending of a word is a consonant or a hard vowel (а, о, у, ы, э):
дом (house)
полка (shelf)
вино (wine)
Soft stems end in a soft consonant. In this case the ending of a word is й, ь or a soft vowel (я, ё, ю, и, е):
музей (museum)
море (sea)
дверь (door)
The hardness and softness of a stem define what ending we add when we conjugate words.