JSX (JavaScript XML) is an extension to the JavaScript programming language that allows developers to write HTML-like syntax inside of their code. It enables them to create React components with a more succinct and intuitive structure than regular JavaScript would allow. JSX makes it easier for developers to read and understand their code, as well as provides a streamlined development process when creating UI elements in React applications. Additionally, using JSX instead of plain JavaScript significantly reduces the amount of time needed to debug and spot errors. 

The primary benefit provided by JSX is its ability to make writing complex user interfaces much simpler and faster than before. By allowing developers to use HTML-like syntax within the same file as their React components, they can generate UIs quickly without needing extensive knowledge on how each individual element needs be coded from scratch in pure JavaScript. Furthermore, it also allows for improved modularity within projects since all related components are written together in one file - making organization easy while ensuring compatibility between different parts of an application's UI design system at once! 

First, let's look at a simple example of JSX. Here's a React component that renders a heading: 

import React from 'react'; 
function FirstHeading() { 
return <h1>Hello, React!</h1>; 
} 
export default FirstHeading; 

As you can see, the JSX code <h1>Hello, React!</h1> is used to create a heading element. This is similar to writing <h1>Hello, React!</h1> in HTML. 
JSX elements can also have attributes, just like HTML elements. Here's an example of a component that renders a button with a custom class name: 

import React from 'react'; 
function MyButton() { 
return <button className="my-button">Click me</button>; 
} 
export default MyButton; 

Notice that we use className instead of class in JSX, because class is a reserved word in JavaScript. 
You can also use JSX to render dynamic content. Here's an example of a component that renders a list of items passed as props: 

import React from 'react'; 
function MyList({ items }) { 
return ( 
<ul> 
{items.map((item) => ( 
<li key={item.id}>{item.name}</li> 
))} 
</ul> 
); 
} 
export default MyList; 

In this example, we use the map method to loop through the items array and create a list item for each item. We also use the key attribute to give each list item a unique key, which is a best practice in React when rendering a list of items. 
One important thing to note is that JSX must be transpiled (converted) to JavaScript before it can run in a browser. This is typically done with a tool called Babel. With this tool, you can write JSX in your React components and it will transpile it to JavaScript that the browser can understand.