Prefetching
Beginner
Fetching data before the program asks for it, by guessing what it will need next.
Novice
Bringing lines into the cache ahead of demand. Hardware prefetchers spot patterns, such as a stream of consecutive lines or a fixed stride, and fetch the next ones; software can also issue prefetch instructions.
Expert
Judged by accuracy (useful ÷ issued), coverage (misses removed ÷ original misses) and timeliness (arriving before use but not so early it is evicted). Distance must cover latency ÷ time per access; useless prefetches cost bandwidth and pollute the cache.
Explained in Caches and coherence (Architectures).
See also: Cache, Locality (temporal and spatial).