There are many types of caching that will improve website performance. Here are just five:
Every read query that Symphony executes is cached by MySQL. It is important to understand that this is not the result of the query, but the SQL statement itself. MySQL retains a pool of these statements so that they are quicker to execute in the future. This is pretty standard, and you can use it in your own applications too by using SELECT SQL_CACHE for your read queries.
Once the database has been queried, the results are used to build objects (pages, data sources, sections, field, entries etc.). These objects are alive only for the lifespan of each page, and are destroyed at the end of each request. Systems such as Wordpress allow these objects to be cached and persisted between each page request (using APC, Memcache, flat files or MySQL), thereby shared between all users. Symphony doesn't do this, but it really should.
If you have one piece of a p