Something is "rendered" when it is depicted in a different form. When you open a web page, your browser is rendering the html code for you. Recording programs typically render the data that represents sound as it would appear on oscilloscope.

Audio is just a collection of numbers so the numbers:

0, -10, -15, 17,-20, -17, -15, -10, 0, 10, 15, 17, 20, 17, 15, 10, 0 might look like this: