Everything begins with a journal file---the anatomy of which is covered
in detail in chapter one.  To review: a @emph{journal} contains one or
more @emph{transactions}, each of which refers to two or more
@emph{postings}.  A @emph{posting} specifies that a given
@emph{amount} is added to, or subtracted from, an @emph{account}.
(@emph{Accounts} may be nested hierarchically by separating the elements
using a colon).  Lastly, an @emph{amount} is a figure representing a
given @emph{quantity} of a @emph{commodity}.  Here follows a review of
these terms, which are all used extensively throughout this chapter:

@table @emph
@item journal
A journal is a data file containing a series of transactions.

@item transaction
a transaction relates a group of two or more postings, with the absolute
constraint that the total sum of a transaction's postings must equal
zero.  That is, every transaction in a journal must @emph{balance} to zero.

@item posting
Postings record how commodities are moved between accounts.  If you
spent money on a movie ticket, for example, such a transaction would have two
postings: One to show how the money was taken from your wallet, and
another to show how it was applied to your movie expenses.

@item account
An account 

@item amount

@item quantity

@item commodity
@end table