Apple silicon architecture is designed to get background processes out of the way of our apps running in the foreground, by using the E cores.

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Apple silicon Macs achieve superior performance by using Efficiency cores to handle background processes, keeping Performance cores available for user applications. The architecture leverages Quality of Service (QoS) metrics to segregate foreground threads (which run on P cores) from background threads (restricted to E cores). This design, inherited from iPhone development and based on ARM's big.LITTLE architecture, prevents background tasks like Spotlight indexing and system services from interfering with user apps, unlike Intel Macs where all processes compete for the same cores. The separation ensures responsive performance and better battery life, even when hundreds of background processes are running.

Last Week on My Mac: Why E cores make Apple silicon fast