1. What is a declarative UI structure and how does React support this idea?
   2. Declarative UI structures define what the UI component is instead of worrying about how it is defined. React supports this idea by allowing components to be declared using JSX syntax.
2. How does React improve rendering performance?
   1. React has a virtual DOM that compares changes made to components' data in memory, avoiding the browser DOM when possible. React 16 has a new internal architecture that allows rendering to be split up into smaller chunks of work and prioritized.
3. When would you render a fragment?
   3. Fragments are used to avoid having to render unnecessary DOM elements