This 5V regulator circuit provides 5A load current capability, well above the current limit of the linear regular component itself. This is thanks to the load sharing role of the bypass PNP transistor.
The circuit is shown with a household 120 V. AC input, with a transformer and rectifier circuit, attempting to approximate a 12V automotive input voltage level. The design is based on an example application circuit shown in Figure 11 of the On Semiconductor Datasheet MC7800/D, November 2014 - Rev. 27. This executable design can be used to assess line and load transients, efficiency, PSRR vs. Frequency, etc. It can also be used for selecting the peripheral circuit components to achieve the desired performance.
See also http://www.systemvision.com/design/ac-dc-power-adapter for a lower power level circuit.