I read Cecil’s answer at http://www.straightdope.com/classics/a1_126b.html, but I’m still confused.
Is the four-color map problem about the actual countries of the world – real maps? Or is about theoretical maps?
Because if it’s about theoretical maps, it seems quite easy to envision a map that needs five colors.
There must be something I’m missing.
Sorry, the URL works if you remove the comma.
Nope, it’s theoretical maps, and the thing you’re missing is that your intuition plays tricks on you. Go ahead and try it. Draw out a map. Then color it in as best you can.
LOL! Since Cecil was of no help, I found other sites that explained two things to me. One, theoretical maps count. Two, my efforts at creating maps requiring five colors were futile, and when I thought I had one it was because I was using a color unnecessarily. 
Thanks anyway!
Two points to remember:
(i) In real maps, the sea is painted blue and no land masses can be coloured that shade. These restrictions do not apply in the 4-colour theorem.
(ii) In real maps, separate parts of one country must be the same colour. Again, this does not apply in the theorem.
With these restrictions, I would recommend Achernar’s advice. Try and construct a counterexample.
An excellent introduction to the four color theorem may be found here. It’s got lots of pretty pictures.