Historically, a cursor was a lit area on a computer screen that winked off and on. The name came from engineers who had to design a circuit to do this. The display has eight rows, or lines. The top two lines are usually reserved for labels, and the cursor can't go there. That means the cursor can only go on one of six lines at the most.
Some screens use fewer than six lines, some as few as two.
There are two buttons, one above the other, located between the Value buttons and the Letter buttons. They are used to change what line the cursor is on. If the cursor starts on the top line, pushing the DOWN button moves it down one line at a time. When it gets to the bottom, it will wrap around and go back to the top line. Likewise, pushing UP enough times will bring you right back where you started.