The eraser tool will only remove the formatting on your text, not the text itself. So if you copied your content in from an email or a website and the format is not quite the way you want it, you can just click on the eraser tool to set the text back to the default style you set up in the style editor.
Say that this (below) is your original text. And you don't want all of that funky colors and formatting.
Just highlight your text and click on the eraser tool. 
And your text will look like this - funky colors and weird formatting gone!
Note
The eraser tool doesn't work for content pasted in from Microsoft Word. If you copied in your content from Word, the eraser tool can't always get rid of all the junk code in the background. Use the "paste from word" option on the toolbar for better formatting results.