Disposable income is important to households for several reasons. It is the money left after taxes for paying for mortgages, household bills and other regular outgoings. This money can also pay for essential travel and things like fixing cars and home maintenance. It is vital you have enough disposable income to pay your monthly home rental/mortgage bills or you can risk eviction from your home.
Discretionary income is what's left after your regular outgoings. This money can be used to treat yourself to a host of things from flights to holidays to new clothes or a new car. The amount of disposable income and discretionary income you have depends on what salary you are taking home from the company you are working for, how much you pay in taxes and what your regular outgoings are. Be careful, as you do not want to overspend and leave yourself with no money to buy food to eat!