About the Eraser Tool
The Eraser tool is pressure sensitive, like the Brush tool, giving you more precision when erasing parts of a drawing. You can also use the Select tool to select drawing objects and delete them instead of erasing.
It is a good idea to create and save erasers with precise sizes and parameters to save time when drawing and designing. There are two icons located at the top-right corner of the Eraser properties window: New Brush Preset is for creating a new preset and Update Preset is for updating the currently selected preset. Use them after you have set all the parameters for the new eraser preset.