Elements & Elementals
The ancient Greeks believed that the material realm was made up of four elements - earth, air, fire and water.  The spiritual realm consisted of Aether/Akasha - the fifth element.  In paganism, this concept is used in magick and ritual.  During ritual the elements are called upon to give power and protection.  Each part of the circle (north, south, east and west) is represented by a different element and each element can be represented by a number of things.  Click on the pictures below to find a table of correspondences for a specific element.

Elementals are considered to be spirits which embody one of the elements.  It is possible to summon them during ritual and some people even believe it is possible to see them. 
Personally, one of the first things to do when starting out in witchcraft is to familiarise yourself with the elements thoroughly.  The best way to do this is to experience them using something we all have - the five senses.  For air, you can listen, watch and feel it's movement all around us.  Activities such as flying a kite can make the experiences that bit more interactive.  To experience earth, cultivate a garden, learn to recognise trees and flowers, go into caves and climb mountains.  All these increase our appreciation of the land.  For Fire, you can build bonfires (sensibly of course), learn to build and cook upon an open fire as well as experimenting with spicy food.  Finally, to experience water you can go sailing, swimming and diving or even just sit and watch the waves crashing onto a beach.  It's all about using your imagination and getting to know the energies that you are eventually going to be working with.