InnoDB stores all records inside a fixed-size
unit which is commonly called a "page" (though
InnoDB sometimes calls it a "block" instead).
Currently all pages are the same size, 16KB.
A page contains records, but it also contains headers and trailers. I'll start this description with a high-altitude view of a page's parts, then I'll describe each part of a page. Finally, I'll show an example. This discussion deals only with the most common format, for the leaf page of a data file.