That's from Official React page. What does it mean?
What is that?
Things happen really fast since we don't have to wait for the server to respond to render a new page or something new.
Next comes the user interfaces part.
User Interfaces are basically what the users see and with React we use components for building these interfaces.
We can split any web page into components. For example, the header of the page, the body of the page, sidebar, and footer. We can split any webpage into these components – header component, sidebar component, footer component etc.
So how is this useful?
When we split up a web app or website into components, we can build these smaller pieces of building blocks which then makes up the whole structure.
Instead of making our web app or website as a whole big structure, we create all these smaller things on contained on their own. This makes it really easy to maintain and update code. It's also helpful in team works.
Now, let's say we have to change something in our sidebar component. Instead of going through a big pile of code for our web page, we can just go on and change the sidebar component.
We can also reuse these components. For example, let's say, we have a component which shows some kind of a form on our webpage. Now, we want to show the form somewhere else. Instead of coding it, again and again, we can just code it once and then use the component wherever we want to use.