Caching

Caching is keeping a copy of something you use often somewhere quick to reach, so you do not have to fetch or rebuild it from scratch each time. A website caches its pictures in your browser, so the second visit loads far faster than the first.

It is like keeping everyday mugs on the counter instead of the top shelf: the things you reach for most are nearest to hand. Caching matters because it makes systems feel fast and cheap to run, though it needs care so people are not shown an out-of-date copy after something has changed.