Just as the name implies, push sticks are used to increase safety margins while guiding workpieces through powered table tools such as saws, planers, and routers. Do you need to use one? Absolutely - if you want to finish your work session with the same number of digits with which you began. 'Nuff said. Here are some good examples for your perusal:

The BEST Push Stick EVER!!! by Jay Bates

The Octo-Push (Part 1: Push Stick Templates) by hffcom

How To Make A Push Stick by John Heisz

Matt Makes a simple push stick by Matt Diresta

How To Make Push Sticks - A Simple, Cheap, & Easy Design by AskWoodMan

Make a Mudflap Girl Push Stick for Your Table Saw by Steve Carmichael