Dongles are not needed to use USB C. However, since most USB devices out there currently don't use USB C yet, a lot of people will be using dongles to handle the various connectors.
Think of USB-C as a differently shaped plug, because that's really all it is. It just happens to be a well designed universal connector that support USB, Thunderbolt, PCI-Express, HDMI, power, ethernet, and DisplayPort--all with one connector. In time, devices and peripherals will all ship with USB-C connectors. But for now, you just need adapters or cables to fit both ends of your connections.
It's called USB Type-C (shortened to USB-C) because it came after the previous two USB connectors, Type-A and Type B.