[From MySQL Developer Zone
If youve been using MySQL for any time at all, you know that a unique advantage afforded MySQL users is the ability to use multiple storage engines to manage the underlying data stored on the server. This efficient and modular architecture provides large performance and manageability benefits for those wishing to specifically target a particular application need such as data warehousing, transaction processing, high availability situations, etc. while enjoying the advantage of utilizing a set of interfaces and services that are independent of any one storage engine. The MySQL server supplies engines that are internally developed, provided by third-party software vendors, and also allows a user to build their own storage engine if they desire.
The article continues at