To understand this feature better, Lets take an example of Banking transactions.
I am from India . Currently working in Netherlands. I usually transfer money from my NL account to IND account almost every month.
Deduction from my NL account and Credit into my IND account are part of a single transaction.
What does it mean ?
It means that if any failure occurs in between deduction and credit , the whole action should be rolled back.Read more here.