What are Intermediate Points in Geography?  What is land and water
between 23.5 degrees N and 23.5 degrees S called?  What is the most
northern point on Earth?

Hi Ciao and thanks for your question!

The intermediate points in geography are those points on a compass
that are halfway between the cardinal points.  The cardinal points are
north, south, east and west.  The intermediate points are northwest,
southwest, southeast, northeast.

Here is a website that shows the cardinal and intermediate points on a
compass and defines a number of other compass-related terms:
http://www.geog.port.ac.uk/webmap/hantsmap/hantsmap/cmprose.htm

The land and water between 23.5 degrees north and 23.5 degrees south
is referred to as the tropics.  The line that runs at 23.5 degrees
north of the Equator is known as the Tropic of Cancer and the line
that runs at 23.5 degrees south of the Equator is known as the Tropic
of Capricorn.  The tropics are the two lines where the sun is directly
overhead at noon on the two solstices.  Around June 21 the sun is
directly over the Tropic of Cancer and around December 21 the sun is
directly overhead the Tropic of Capricorn.

Here's a nice website that shows the tropics:
http://www.worldatlas.com/aatlas/imagee.htm

and here’s another website that has some good info on the tropics:
http://geography.about.com/library/misc/blequator.htm

The northern most point on Earth is called the North Pole.  It has a
latitude of 90 degrees. That's as far north as one can go!  Here is a
neat map of the North Pole:
http://www.athropolis.com/map2.htm

Interestingly, compasses do not point directly to the North Pole. 
Rather they point to what is called the "magnetic north pole" which is
slightly to the south of the actual north pole (they are currently 966
km apart).  The magnetic north pole moves around slightly from year to
year due to secular variation, however the north pole always remains
in the same place.

For more on the magnetic north pole and its migration see:
http://deeptow.whoi.edu/northpole.html

Search terms:
"intermediate points" geography
tropics 23.5
"north pole"
"magnetic north pole"

If you have any questions regarding this answer please do not hesitate
to request clarification.

Best of luck!

-blinkwilliams-ga