This all probably seems insultingly simple so far, but do not be led into skimming. Things will get more complicated soon. Also, do not try a new command until you are told it is time to. Otherwise, you may make Info skip past an important warning that was coming up. This is a big node and it does not all fit on your display screen.
Space moves forward, to show what was below the bottom of the screen.
When you type the space, the two lines that were at the bottom of the screen appear at the top, followed by more lines. Delete 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 type Space when there is no more to see, it rings the bell and otherwise does nothing. The same goes for Delete when the header of the node is visible. To move back to the beginning of the node you are on, you can type a lot of Deletes.