The biggest single (and most basic) difference between business and public administration is that the former relates to the private sector, whereas the latter is concerned with the public sector.
As the name implies, business administration deals with the operation of a business, a corporate entity concerned with making a profit. Public administration, on the other hand, is related to the implementation of policy goals by government departments and nonprofit organizations such as charities. If business administration is primarily concerned with the bottom line, with making a profit, the focus of public administration is on delivering certain policy objectives.
To be sure, business and public administration share similar concerns. Both disciplines, for instance, are generally concerned with maximizing efficiency. In the case of the private sector, however, such efficiency is deemed essential for improving the bottom line, whereas in the public and nonprofit sector, it is considered an essential prerequisite to ensuring that policy goals are implemented smoothly.
In recent years, however, the distinction between business and public administration has become somewhat blurred, as governments, in a bid to save money, have attempted to apply the disciplines of business to the operation of the public sector.
Although the overriding objectives of the public sector remain the same, the methods they use to achieve those objectives greatly resemble those of the private sector in generating a profit. The hiring of business executives by government departments in order to improve overall levels of efficiency is one way in which the values of the public sector have become increasingly commercialized.