What is a USB-C active cable?

A passive USB cable is passive because it merely carries the data that's transferred through it. It does not interact with it beyond sending it from one device to another. 

An active USB cable is something else. At one, or sometimes both ends of an active USB cable, are small electronic circuits which boost the intensity of the data being carried by the cable. This can go a long way to warding off signal degradation due to attenuation. 

What benefits are there by using Passive cables and adapters?

Passive Cables, Adapters and Switches have a huge advantage when working with content-protected source devices (ie: HDCP, Macrovision). Because there is only copper wire between the source and display, your signal is never processed by hardware or software which may adjust or strip important data from the stream.

We find that when working with sources like Apple TV, Foxtel, Austar and similar Pay-TV services.

And because Passive products don’t require any extra power, there is no standby usage or requirement for a mains wall socket. They’re simply plug and play, and your AV hardware won’t even know they’re there.

What are the benefits of using Active adapters and converters?

Active products have a huge advantage when working with long cable runs and video conversion applications. Because they take power from an external source, they have the grunt to boost your AV signals over longer distances. This can be important when working with mobile devices running on battery power, as they may not have the output strength to support, for example, a 20m HDMI cable on their own.

In terms of video converters, active units generally have upscaling hardware inside to improve your image. If your source device is standard-definition analogue and your display is Full HD or 4K, the extra processing grunt can make the image quality more bearable.

Finally, Active products are generally more powerful, which gives us splitters and matrixes which can power 2, 4, 8 and more screens at once while maintaining maximum audiovisual fidelity (passive devices are generally limited to a single screen).