Why does my floating point value have an `E` character when I convert it to a string?

txtDebugLog.Invoke(new MethodInvoker(delegate()
{
    fps.Frame();
    ggg = fps.GetFPS();
    txtDebugLog.Text = String.Format("{0}\r\n{1}", ggg, txtDebugLog.Text);
})

txtDebugLog is a TextBox.

Using a breakpoint i see on ggg in this example it's value is:

0.00000102593151

Then i click on continue and see in the TextBox:

1.025932E-06