JavaScript is a scripting language that can be used on a webpage to add dynamic aspects to it. For example, content can be changed using JavaScript, HTML attributes, elements can be accessed and values can be changed, and styles can be modified. It can also be used to call APIs to receive or send information to a backend.
The script tag defines a section within the page where the JavaScript can be placed. The script tag can be placed both in the head and the body tags of the documents. The JavaScript functions can be defined within the script block or it can be called from an external location.
The JavaScript functions defines a code block that executes in response to an event. An event occurs when the user does something, for example, the user can click on a button or on a div element or scroll to the bottom of the page, etc and JavaScript functions can be wriiten to respond to these events.
JavaScript can be defined both on the page or called from an external location. There are some scenarios where it is better to create external file to store all the JavaScript functions and sometimes it might be better to store it on the current HTML page.