This tutorial will teach you how to use a chamfer vertex function and an explanation of how it works.
For this tutorial, create a cube in your scene. Go to window>create polygonal primitives>cube. Since "history" is a big part of this tutorial, we need to make sure history is on and then delete the current history to give us a clean slate.
Step two - Go to edit>delete all by type>history. Set the menu set to polygons.
Select one of the vertices on the cube and go to edit mesh>chamfer vertex.
Like its description says, it "replaces a vertex with a flat polygon face". Select the cube and go to window>attributes editor.
You'll notice there are two important tabs that we'll be looking at: deleteComponent1 and polyChamfer1. Go to the tab polyChamfer1.
The width attribute controls how wide the flat face will be. There are two fields that seem pointless to have, because their values are locked and you can't change them. This is all because of the way that chamfer works in Maya. It's actually extruding a vertex, deleting the extruded vertex, and leaving the vertices that make the base. Now I will show you how to do this yourself, without using the automated chamfer vertex function.
Go to the tab polyExtrudeVertex1. This is the same thing as the polyChamfer1 tab, except that it's in its original form.
Also lock the divisions option.
Now basically you've done the same thing as chamfer vertex, just with more steps. To prevent any confusion, there's no advantage to going either way, ecxept that using the chamfer option automates the procedure and makes it faster.
Hope this tutorial has taught you something or showed you something interesting. There are other functions in Maya that are like the chamfer tool that use other built-in features in Maya to achieve a different goal, like groups (actually, just creating a transform node and making it a parent), subdivide proxies, etc.