CSS and JavaScripts Third-Party packages

 As a Web Developer, you will typically write more CSS and JavaScript code than HTML code.

What & Why 

You can write all the CSS / JS code on your own 

But often, you have certain features, styles, or tasks that are very common to a lot of projects

Default styles 

Image Carousel 

Parallax Effect  

Third-party packages "provide" ready-to-use code that you can add to your projects and sites

Popular CSS Packages & use-cases

Boostrap 

A very popular CSS framework (package) that provides dozens of pre-built component styles (eg buttons, alerts, etc)

Material UI 

A popular CSS framework (package) that provides dozens of pre-built component styles(eg buttons, alerts, etc) which follow the Material design specification by google

Tailwind CSS

A popular CSS framework (package) that provides dozens of pre-build utility styles which you can combine to style your HTML code without writing (a lot of ) custom CSS code.

Popular Javascript Packages & use-cases

Unlike with CSS packages, it's less about choosing "one package for everything"

Image Carousel

Animates image gallery that can be cycled through via page controls. 

Scrollspy

An indicator (an outline) that shows the user where on the page he/she is.

Parallax Effect 

A visual scrolling effect where different elements are animated at different speeds or without different effects.

Third-party vs Custom code 

Third-part

Less code to write, see results quickly 

But: Less control, more default behavior 

Custom Code

More code to write, more work to do, and possibly more error-prone

But: Full control over the result 

There is no single right or wrong way 

Typically in bigger projects, you'll use some third-party code for some parts of your project and custom code for other parts.