The webpage itself is a component of full websites, so let's first talk about the page.
A webpage is similar to how you arrange a magazine page; you have pictures, titles, text paragraphs, and other bits and bobs. They are arranged by the creator in a certain way using containers and styles.
Static assets
By default you put static assets into these containers, such as a page title, or a picture. The containers have sizes and positions and most importantly they are either inside another container, or has containers inside them.
You can imagine a webpage full of boxes inside boxes inside boxes inside boxes, on a 2 dimensional plane.
Dynamic assets
Sometimes, you only have the containers set up, the contents that go into these containers are decided when the webpage is loaded when the user opens it up. Say you have a realtime weather data, that can't be decided beforehand so what happens is that after the containers are in place, the weather data get pulled from a server, and then put inside the corresponding containers.
These are dynamic assets because they change based on where you open the page, who the user is and when the page is opened.
Styling
There's also styles, this is becoming increasingly important because modern websites are getting fancier. Have you seen website in the early 90s? There's basically no styling, just text on the screen, great times.
Now when you load up a webpage, you are greeted by a graffiti exploding from the top, then shiny edges on the buttons glow and move around when you move your mouse, things come into place or move apart when you scroll the page, and everything has an animation to either slide or fade in and out. All these fancy stuff is done by styling each element inside the container, or the containers themselves.
Scripts
But what happens when you click a button, well the things that follow after you click the button are essentially scripts. These scripts can be as simple as triggering the display of some text, or can be as complex as sending money to your mom across the world.
Scripts are typically written by a developer or workflow builder.