L2SS-434: Mention commands

docs/source/devices/using.rst

@@ -7,7 +7,8 @@ The station exposes *devices*, each of which is a remote software object that ma
 - Many devices manage and represent hardware in the station,
 - It exposes *read-only attributes*, that expose values from within the device or from the hardware it represents,
 - It exposes *read-write attributes*, that allow controlling the functionality of the device, or the hardware it represents,
-- It exposes *properties*, which are fixed configuration parameters (such as port numbers and timeouts).
+- It exposes *properties*, which are fixed configuration parameters (such as port numbers and timeouts),
+- It exposes *commands*, that request the execution of a procedure in the device or in the hardware it manages.
 
 To access a device, one creates a ``Device`` object. For example::