Are libraries essential for building apps?
Are libraries essential to build a website or create games?
Yes. Any code you write will fundamentally become your library.
What ui and ux?
UI is the user interface of any tool that requires input. UX is the user experience of a given interface. For example, an airplane pilot is given an interface to control the aircraft, and the controllers are meaningfully arranged to give the pilot the ability to fly safely. The result of the user experience is determined by the pilot's ability to accomplish a task.
What’s a framework?
A framework is the foundation for deploying multiple functionalities for specific tasks. For example, an airport specifically manages how passengers arrive and depart to a new location by air travel. Similarly, a boating dock specifically manages how passengers travel over water. Here is a list of a few web frameworks out there: Github Frameworks
Do all languages have libraries?
Are libraries essential to build a website or create games? In a way no, but they will make your life much easier if you use them properly.
What is UI and UX? User Experience and User Interface. The first one (UX) is in charge of researching the user and it's context to plan and design the basic structure and flow of any platform, app, etc... The later (UI), using the UX outcome, manages the final design, the look-n-feel of it, as well as all the interactions.
What’s a framework? A library of a coding lenguage. They are very useful when you are developing, helps cut time if you can settle for somewhat generic functions-styles. Personally, I still customize the looks as some of them they can look a bit too generic
Does all languages have libraries? Most of them, yeah. All web development languages I know do.