This tag is for questions about kernel buffer caches, including pipe buffers. These are used to store the recently accessed files and/or frequently accessed files.
I think this is to be expected. The term buffer cache has become less widely used. Modern Unixes implement unified buffer cache. At least Linux developers seem to refer to the page cache instead. One poster told me that an OS with a "unified buffer cache" has no buffer cache anymore, only a page cache :-). (However cached IO is still often referred to as buffered IO).
Should we do something about the buffer tag - to make the tag description more consistent with how it is used - or the other way around - or to simply avoid using it?
(I don't think we need to start using a specific tag for "page-cache", though maybe you disagree :-)