What is a USB 'header' (and how is it different from a port)?

With the prevalence of USB devices, it might be easy to mix up USB headers and ports, but there is a key difference between ...
EDN

An open, scriptable USB interface for host driven electronic experiments

SigLab is a combination of open hardware and FOSS (free and open source software) projects to provide easy to use and full featured scriptable USB interface for digital electronic experiments. SigLab ...
EDN

USB on-the-go: opening up consumer/PC connectivity

The On-the-Go (OTG) Supplement to the USB 2.0 Specification opens up a vast range of exciting functionalities for USB-enabled devices in many embedded and consumer devices. Traditionally, USB has ...