+It does so with the assistance of a @dfn{debug adapter}, which is
+a small hardware module which helps provide the right kind of
+electrical signaling to the target being debugged. These are
+required since the debug host (on which OpenOCD runs) won't
+usually have native support for such signaling, or the connector
+needed to hook up to the target.
+
+Such debug adapters support one or more @dfn{transport} protocols,
+each of which involves different electrical signaling (and uses
+different messaging protocols on top of that signaling). There
+are many types of debug adapter, and little uniformity in what
+they are called. (There are also product naming differences.)
+
+These adapters are sometimes packaged as discrete dongles. which
+may generically be called @dfn{hardware interface dongles}.
+Some development boards also integrate them directly, which may
+let the development board can be directly connected to the debug
+host over USB (and sometimes also to power it over USB).
+
+For example, a @dfn{JTAG Adapter} supports JTAG
+signaling, and is used to communicate
+with JTAG (IEEE 1149.1) compliant TAPs on your target board.