When someone mentions about “bread and butter”, you should understand that they are stressing thing or the way they make money for living.
For instance: That online service is her bread and butter.
– You might face “Breadwinner” sometimes. Breadwinner is the person who earns potential salary in a family.‘She is the only breadwinner in the house so she needs a good night’s sleep.’
‘Bread and water’ is the most minimal meal possible such a punishment or hardship.
‘If you gets in the same trouble again, it will be bread and water for a week.