How the LWC HelloWorld Works
Lightning comes with a built-in robust style library. In the HTML (Template) file we use
one of the built in styles (class="slds-m-around_medium" ) to give a
default Lightning-style margin around most of the HTML content.
The heavy lifting of HelloWorld can be traced to the lighting-input
field in the HTML file. The lighting-input field uses the
onchange attribute to listen for a change to its value. When the
value changes, the changeHandler() function in the JavaScript file
executes.
To bind the changeHandler() function to the template, we use the same
syntax with the curly braces: {changeHandler}.