Caching in code igniter

From wikipedia :

... a cache is a collection of data that duplicates the original values ​​stored elsewhere or previously computed, where the original data is expensive to retrieve or compute compared to the cost of reading the cache.

The cache allows you to trade relatively expensive operations (e.g. complex / multiple requests) for less expensive ones (file read / from memory). In dynamic websites, the cache is often used just for this purpose (IO of the database for IO input).

Caching is useful when specific data is frequently read but rarely updated and can be shared with many queries. Blog posts are a great example of this (created once, edited multiple times, read many times).