What is the DC volts?

DC voltage refers to "direct current," and it can mostly be found in batteries. It means that it flows constantly through the circuit, as opposed to AC (alternating current) which switches flow quickly. There are benefits and downsides to direct current, the benefits being that it is best suited for low-current applications and is easy to work with, the downside being that it loses energy quickly as it flows and cannot reach very high power (voltage).

In this context, 'd.c.' is being used as an adjective to describe the nature of the voltage.