Impersonal constructions in Russian
Every English sentence has a verb, a part of speech which denotes an action (to read), an occurrence (to decompose) or a state (to exist). In Russian, there are many constructions which do not require the use of a verb in a sentence. Such constructions often describe emotional or physical states, for example Ему холодно He is cold, Здесь скучно It's boring here, Мне нужно идти I need/I have to go, Мне можно войти? May I come in?. As you can see, English uses verbs in these phrases (is, need, have to, may).
Russian does not use verbs in these constructions, it uses adverb-type words, usually ending -о (холодно, скучно, нужно, можно). These Russian constructions have no subject and are called impersonal constructions. The person who is affected by the described state is marked by a word (noun or pronoun) in the dative case form, so literal translation of the above examples would be:
Ему холодно. – I'm cold. literally: To him is cold.
Мне нужно идти. - I must go. literally: To me is necessary to go.
Мне можно войти? - May I come in? literally: То me is possible to come in?