bread and butter

Translations
основной источник дохода
Writing is her bread and butter.
Писательство - это её основной источник дохода.
Definitions
A phrase that refers to the basic means of livelihood or the primary source of income for someone, often implying the essential or fundamental aspects of a person's work or life.
Words
bread

noun
хлеб
and

conjunction
и
butter

noun
масло