Informal vocabulary is used in one's immediate circle: family, relatives or friends. One uses informal words when at home or when feeling at home.
Informal style is relaxed, free-and-easy, familiar and unpretentious. But it should be pointed out that the informal talk of well-educated people considerably differs from that of the illiterate or the semi-educated; the choice of words with adults is different from the vocabulary of teenagers; people living in the provinces use certain regional words and expressions. Consequently, the choice of words is determined in each particular case not only by an informal (or formal) situation, but also by the speaker's educational and cultural background, age group, and his occupational and regional characteristics.
Informal words and word-groups are traditionally divided into three types: colloquial, slang and dialect words and word-groups.