Help compiling using makefile

I have found a program listed on this web page regarding the Sun, Earth and Moon.

It is called sem.c

I would really like to run the code and see the output, but I am struggling with this.
What is the makefile stuff all about and how do I just get it to run?

Thank you for any assistance

This looks like an interesting page with well know tutorials.
I imported the file sem.C. However it uses internally 3 files (earth.dat. sun.dat, moon.dat) that are now available on this web page.
If you can find these 3 files (let me know), then you can run the script (see attachment) from interactive ROOT with
root > .x sem.C
root > .x sem.C(0.03,1.1) , etc

sem.C (4.48 KB)