7805 is a 5V Voltage Regulator that restricts the voltage output to 5V and draws 5V regulated power supply. The 7805 is the most common, as its regulated 5-volt supply provides a convenient power source for most TTL components.

7805 is a series of 78XX voltage regulators (as known as L78xx, LM78xx, MC78xx…), the xx is replaced with two digits, indicating the output voltage (for example, the 7805 has a 5-volt output, while the 7812 produces 12 volts