In Bolt Iot course has mentioned about html then what is the use of html language into the iot projects.
Using of temperature sensor and BOLT IOT device we can collect the data of temperature. but when we want to visualize it on the web we need HTML.
HTML - Front End
Sensors and IOT Devises - Hardware
HTML is used to show the world the output, in this case html is helpful like suppose a case in which your iot device need to fetch some data from the internet, to show what data is used and from where html is used and it acts as a front end. Another case is to show others the output of your iot device which can be used later by others, it helps in Data Visualization.
Bolt has provided a standard user interface that the users can use to interact with iot devices from your laptop or smartphones.
But in case you need a different user interface that can suit your purpose better, in this case html can be used to create the user interface.