Rounds/Chamfers add or remove material by creating smooth transitions between existing geometry. When creating These features on a model, Creo Elements/Pro awaits the selection of edges and/or surfaces to be used as references. These tool adapts according to the references that you select to create the round feature.
In this tutorial I will try to explain (with a very simple example) how You can use Round/Chamfer Tool.
The types that I have explained are listed below.
=>Round tool section
1.  Creating Round using  edges
2.  Creating Round using surface and edge
3.  Creating Round using two surfaces
=>Chamfer Tool section
1.  Creating Chamfer using edges
2.  Creating Chamfer using surface and edge
3.  Creating Chamfer using two surfaces