elisp: Buffer Basics
26.1 Buffer Basics
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A “buffer” is a Lisp object containing text to be edited. Buffers are
used to hold the contents of files that are being visited; there may
also be buffers that are not visiting files. Although several buffers
normally exist, only one buffer is designated the “current buffer” at
any time. Most editing commands act on the contents of the current
buffer. Each buffer, including the current buffer, may or may not be
displayed in any windows.
Buffers in Emacs editing are objects that have distinct names and
hold text that can be edited. Buffers appear to Lisp programs as a
special data type. You can think of the contents of a buffer as a
string that you can extend; insertions and deletions may occur in any
part of the buffer. 
Text.
A Lisp buffer object contains numerous pieces of information. Some
of this information is directly accessible to the programmer through
variables, while other information is accessible only through
special-purpose functions. For example, the visited file name is
directly accessible through a variable, while the value of point is
accessible only through a primitive function.
Buffer-specific information that is directly accessible is stored in
“buffer-local” variable bindings, which are variable values that are
effective only in a particular buffer. This feature allows each buffer
to override the values of certain variables. Most major modes override
variables such as ‘fill-column’ or ‘comment-column’ in this way. For
more information about buffer-local variables and functions related to
them, see Buffer-Local Variables.
For functions and variables related to visiting files in buffers, see
Visiting Files and Saving Buffers. For functions and
variables related to the display of buffers in windows, see
Buffers and Windows.
-- Function: bufferp object
This function returns ‘t’ if OBJECT is a buffer, ‘nil’ otherwise.
Info Catalog
elisp: Buffers
elisp: Current Buffer