Ans. Emmet gets you code snippets in the code editor itself with the help of some unique expressions that are very helpful for some Boilerplate codes and saves typing as well.
Ans.
To answer this we will start with "You tell libraries what to do, frameworks tell you what to do."
So a library should be used in a large scale web application where the need is to make the application big so wherever you are going in the application you should use best practices with your code. Small applications don't need framework, it will be more writing the boilerplate codes.
On the other hand libraries are mostly for a single purpose for e.g. React creates UI, Redux handles state management, Jquery provides cross browser dom manipulation, so libraries are built for a single focus but you have 100% control over there you determine how you do it add only the things you need but at a large scale custom functionality can hurt you specially if you are doing it first time.
Ans. A CDN is content delivery network, It is a network of servers that shares content from an origin server to the world so basically first it gets the content and then shares the same content with other servers across the globe, by this the latency of the content reduces and user get the content fast and server are also distributed so they also feels less stress.
Ans. React is called react because of its quick and easy way of updating the DOM so when the first time any component is initialized the render method is called that generates a light weight representation of your view, from that representation, a string of markup is created and injected into the document when the data changes and the render method is called again so it diff the return value from the previos call and returns only the minimal set of changes.
Ans. CORS stands for cross origin resource sharing, CORS is used to allow cross origin requests to be made from another domains by default its set to "same-origin", It is used to check whether it is safe to allow sharing the resource from other domain, The resources may include the audio, video, images, link or scripts that specifies weather to support the request or not.
Ans. So the react library is responsible for creating React components and the reat dom