InnoDB page has seven parts:
Infimum + Supremum Records
As you can see, a page has two header/trailer pairs. The inner pair, "Page Header" and "Page Directory", are mostly the concern of the \page program group, while the outer pair, "Fil Header" and "Fil Trailer", are mostly the concern of the \fil program group. The "Fil" header also goes by the name of "File Page Header".
Sandwiched between the headers and trailers, are the records and the free (unused) space. A page always begins with two unchanging records called the Infimum and the Supremum. Then come the user records. Between the user records (which grow downwards) and the page directory (which grows upwards) there is space for new records.