I'm indebted to the website Techradar for the following explanation of NPU. I'm an occasional watcher of a tech programme on the BBC aimed at the layman - nice simple explanations of complicated things.

Todays explanation of NPU got me though so I went on Google to find out more :

An NPU, or Neural Processing Unit, is a dedicated processor or processing unit on a larger SoC designed specifically for accelerating neural network operations and AI tasks. Unlike general-purpose CPUs and GPUs, NPUs are optimized for a data-driven parallel computing, making them highly efficient at processing massive multimedia data like videos and images and processing data for neural networks. They are particularly adept at handling AI-related tasks, such as speech recognition, background blurring in video calls, and photo or video editing processes like object detection.

Thanks for that ... none the wiser