一、研究数据库的人这样理解：http://wenku.baidu.com/view/32b8b13e376baf1ffc4fad7e.html
Cache和Buffer是两个不同的概念，简单的说，Cache是加速“读”，而buffer是缓冲“写”，前者解决读的问题，保存从磁盘上读出的数据，后者是解决写的问题，保存即将要写入到磁盘上的数据。在很多情况下，这两个名词并没有严格区分，常常把读写混合类型称为buffer cache。
A buffer is something that has yet to be "written" to disk. A cache is something that has been "read" from the disk and stored for later use.
二、编程序的人最好这样理解：http://wiki.answers.com/Q/The_difference_between_buffer_and_cache
Think of it like this: a “Buffer” is an area where data moves back and forth between two objects. A “Cache” is where data is stored when it may not be immediately needed, but might be soon. A buffer is like a hallway between two rooms, and a cache is like a closet. Get it?