Concurrent Mode changes how React renders components in a few important ways:

1. Rendering is Interruptible

   • React can pause a render midway if something urgent (like a click or keypress) happens.

2. Multiple Renders are Possible

   • React might start rendering one version of the UI, but if new props or state come in, it can abandon that render and start over.

3. Prioritization of Work

   • Updates are no longer strictly "first come, first served." Some updates (like user input) are treated as more important.

4. Rendering is Not Always Committed

   • Just because React starts rendering doesn’t mean it will commit it to the screen. Only completed, latest, necessary renders get committed.

5. New Patterns for Developers

   • Because updates can be interrupted or restarted, developers need to write code that is resilient (e.g., avoiding side effects during render).

In simple terms:

With Concurrent Mode, React thinks more like a multitasking operating system — handling urgent tasks first, and finishing background tasks later.

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