What is a buffer?

From Stack Overflow: http://stackoverflow.com/questions/14551006/what-is-a-buffer-in-node-js

A Buffer is a chunk of memory, just like you would have it in C/C++. 
You can interpret this memory as an array of integer or floating point numbers of various lengths, or as a binary string. 
Unlike higher-level data structures like arrays, a buffer is not resizable.

It corresponds roughly to:

char* or char[] in C/C++
byte[] in Java
A mutable bytes or a non-resizable bytearray in Python
Strings in php if they were mutable

Hope that helps :)

Raw data is stored in instances of the Buffer class. A Buffer is similar to an array of integers but corresponds to a raw memory allocation outside the V8 heap.

Buffers are instances of the Buffer class in node, which is designed to handle raw binary data. Each buffer corresponds to some raw memory allocated outside V8. Buffers act somewhat like arrays of integers, but aren't re-sizable and have a whole bunch of methods specifically for binary data. In addition, the "integers" in a buffer each represent a byte and so are limited to values from 0 to 255 (2^8 - 1), inclusive.