The tool options window is whats called 'context sensitive', i.e. what it shows depends on what tool you have selected. In this case its showing a pen brush.

In the top right hand corner is a button next to the 'X' close button which is an auto roll up / pin open button. I keep mine pinned open but you can optionally have the window scroll up to just the title bar until your mouse goes over it where it unfurls.

You can open this window with the 'O' key too or get to it with view / toolbars / tick tool options.

The window contains parameters for that tool. So the size of the pen, what shape, opacity, hardness (i.e. edge fade) and density (stipple effect). The 'step' is the threashold of move before it plops another one down and is in percentage so 5 = 5%. Theres a different set of params for each tool so you will have to try them all to see them.

The window has tabs so that there are more params on the next tab. In this case its for showing precise cursors, brush outlines and pen tablet pressure sensitivity options.