If you take a moment and think about how we, humans, function you will find that we have a 5 senses which are felt by corresponding organs, then the stimuli are sent to the brain via the nerves, finally the brain processes these stimuli. The result is most often knowledge and perhaps also actions can be triggered: the brain then transmits commands via the nerves to muscles which then trigger moving hands, legs, talking, etc.
Now one way of looking at the Web of Things – the way this tutorial looks at it – is to see “things” as organs which detect the stimuli. These are then sent via wireless or wired technology, typically on an IP/HTTP network to processing and storage engines. These engines then crunch the received information and generate knowledge. Sometimes they can also trigger an action such as sending a tweet.
One distinction is that while in the case of the humans the sensors and processors are spatially centralized, in the case of WoT we may be looking at a global distributed system – see the figure below.