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.

sine wave

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:

single cycle sine wave

Background image by Pauline Moss. at