Page cache is used to hold pages that contain the data read/written from disk.
Whenever a file is read from disk, the data is first copied in page in Page
Cache and then to user space buffer.
Similarly , while writing the data is first written to page in page cache and then
to the disk(deferred write).

Buffer cache is now implemented through Page Cache(there is no separate Buffer
Cache now)...those pages that are used as buffer cache in the Page cache are called as "buffer
pages"