Have you ever heard of React (JavaScript Library)
i had not heard about it but learned it is a javascript library for building user interfaces
What does it mean to build a user interface?
its like a way the human and computer interacts, like how your screen looks and where you click on pages 
So is JavaScript a computer language for that?
yes its one of the three core technologies along with html and css on the internet 
Which one is the easiest to learn?  I would love to learn one.
i do not know actually, but i do know html is the standard for creating web pages
So if I want to build websites html is the best?
Adobe Flash
Adobe Flash is a deprecated multimedia software platform used for production of animations, rich Internet applications, desktop applications, mobile applications, mobile games and embedded web browser video players. Flash displays text, vector graphics and raster graphics to provide animations, video games and applications. It allows streaming of audio and video, and can capture mouse, keyboard, microphone and camera input. Related development platform Adobe AIR continues to be supported.
Artists may produce Flash graphics and animations using Adobe Animate. Software developers may produce
React (JavaScript library)
React (also known as React.js or ReactJS) is a JavaScript library for building user interfaces. It is maintained by Facebook and a community of individual developers and companies.
React can be used as a base in the development of single-page or mobile applications, as it is optimal for fetching rapidly changing data that needs to be recorded. However, fetching data is only the beginning of what happens on a web page, which is why complex React applications usually require the use of additional