This node's mode line tells you that you are now at node ‘Help-^L’, and the header line tells you that p would get you back to ‘Help-P’. The node's title is highlighted and may be underlined as well; it says what the node is about.
This is a big node and it does not all fit on your display screen. You can tell that there is more that is not visible because you can see the text ‘Top’ rather than ‘All’ near the bottom of the screen.
The <SPC>, <BACKSPACE> (or <DEL>)1 and b commands exist to allow you to “move around” in a node that does not all fit on the screen at once. <SPC> moves forward, to show what was below the bottom of the screen. <DEL> or <BACKSPACE> moves backward, to show what was above the top of the screen (there is not anything above the top until you have typed some spaces).
>> Now try typing a <SPC> (afterward, type a <BACKSPACE> to return here).
When you type the <SPC>, the two lines that were at the bottom of the screen appear at the top, followed by more lines. <DEL> or <BACKSPACE> takes the two lines from the top and moves them to the bottom, usually, but if there are not a full screen's worth of lines above them they may not make it all the way to the bottom.
If you are reading this in Emacs, note that the header line is always visible, never scrolling off the display. That way, you can always see the ‘Next’, ‘Prev’, and ‘Up’ links, and you can conveniently go to one of these links at any time by clicking the middle mouse button on the link.
<SPC> and <DEL> not only move forward and backward through the current node. They also move between nodes. <SPC> at the end of a node moves to the next node; <DEL> (or <BACKSPACE>) at the beginning of a node moves to the previous node. In effect, these commands scroll through all the nodes in an Info file as a single logical sequence. You can read an entire manual top to bottom by just typing <SPC>, and move backward through the entire manual from bottom to top by typing <DEL> (or <BACKSPACE>).
In this sequence, a node's subnodes appear following their parent. If a node has a menu, <SPC> takes you into the subnodes listed in the menu, one by one. Once you reach the end of a node, and have seen all of its subnodes, <SPC> takes you to the next node or to the parent's next node.
Many keyboards nowadays have two scroll keys labeled ‘PageUp’ and ‘PageDown’ (or maybe ‘Prior’ and ‘Next’). If your keyboard has these keys, you can use them to move forward and backward through the text of one node, like <SPC> and <BACKSPACE> (or <DEL>). However, <PAGEUP> and <PAGEDOWN> keys never scroll beyond the beginning or the end of the current node.
If your screen is ever garbaged, you can tell Info to display it again by typing C-l (Control-L—that is, hold down <CTRL> and type L or l).
>> Type C-l now.
To move back to the beginning of the node you are on, you can type the <BACKSPACE> key (or <DEL>) many times. You can also type b just once. b stands for “beginning.”
>> Try that now. (We have put in enough verbiage to push this past the first screenful, but screens are so big nowadays that perhaps it isn't enough. You may need to shrink your Emacs or Info window.) Then come back, by typing <SPC> one or more times.
You have just learned a considerable number of commands. If you want to use one but have trouble remembering which, you should type ? (H in the stand-alone Info reader), which displays a brief list of commands. When you are finished looking at the list, make it go away by typing <SPC> repeatedly.
>> Type a <?> (or <H> in the stand-alone Info reader) now. Press <SPC> to see consecutive screenfuls of the list until finished. Then type <SPC> several times. If you are using Emacs, the help will then go away automatically. If you are using the stand-alone Info reader, type x to return here.
From now on, you will encounter large nodes without warning, and will be expected to know how to use <SPC> and <BACKSPACE> to move around in them without being told. Since not all terminals have the same size screen, it would be impossible to warn you anyway.
>> Now type n, or click the middle mouse button on the ‘Next’ link, to visit the next node.
 The key which we call “Backspace or DEL” in this manual is labeled differently on different keyboards. Look for a key which is a little ways above the <ENTER> or <RET> key and which you normally use outside Emacs to erase the character before the cursor, i.e., the character you typed last. It might be labeled ‘Backspace’ or ‘<-’ or ‘DEL’, or sometimes ‘Delete’.