To purchase a copy of the book:
50 is for your essentials:
The things you need to survive: mortgage or rent payments, utilities, transportation to work, and groceries.
20 is for your future:
Debt repayment, emergency savings, investments, and retirement savings. How you allocate the 20 depends on where you are in life currently, and what you dream your life will look like 5, 10, 30 years from now.
30 is for your lifestyle:
With the essentials and laying a foundation for your future out of the way, a full 30% of your income is yours to spend on the fun stuff: lifestyle. This includes eating out, travel, gifts, shopping, and so on. How you choose to allocate these is up to you.