Right-click the dividing line between toolbars and select "join area", then click on the one you want to close.
Those little diagonal lines in the bottom left corner of every toolbar is how you create/open new ones. The dropdown menu to the right of that is to change the contents of that toolbar.
Although, there aren't actually any "toolbars" in blender. Everything you see is a window panel. The best way to understand it is just to play around with it. Try dragging the panel control (diagonal lines) up or right to create a new panel, and then drag it down or left to close.