Comprehensive and Detailed Explanation From Exact Extract of Design Expert (CCDE)

Summarization reduces control plane state by abstracting detailed route information. As packets move further away from the destination subnet, the network advertises summarized prefixes instead of individual host or subnet routes, minimizing control plane overhead and routing table size. This helps scale large networks and improves convergence times.

While aggregation and summarization are related, summarization specifically refers to the propagation of route prefixes and their abstraction — making it the precise fit for this question.