There are inputs for your computer and for other digital and analog sources. The USB input uses ‘asynchrounous’ mode to insure the lowest possible jitter (timing errors) from notoriously unstable computer audio outputs and supports 24/96 HD studio master music files. Coaxial and optical inputs allow many different digital sources to be connected, from CD and DVD disc players, to set top boxes like AppleTV or satellite and cable receivers. There are also analog inputs for iPods and older non-digital audio components like FM tuners.
The D 3020, with its wireless Bluetooth capability, can stream music from smartphones, tablets and laptops and even supports the highest audio quality Bluetooth aptX that is becoming more and more popular for its excellent sound quality and low power consumption compared to Wi-Fi.