// dom 
- With the HTML DOM, JavaScript can access
and change all the elements of an HTML document.
- The DOM represents the document as nodes and objects; that way, 
programming languages can interact with the page.



// virtual dom
- The virtual DOM (VDOM) is a programming concept where an
ideal, or “virtual”, representation of a UI is kept in memory
and synced with the “real” DOM by a library such as ReactDOM. 
This process is called reconciliation.