I do not understand Le Chatelier's Principle - please help!

LeChaterlier's principle states: 'If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change'. In short, this helps us to work out HOW changing a factor of the reaction will affect the position of equilibrium. If we have the reversible reaction: 'A + 2B <---> C + D' (where A and B are reactants and C + D are the desired reaction products), Le Chatelier's principle tells us that if we increase the concentration of A the position of equilibrium will move to decrease the concentration of A, i.e. it will move towards the product side of the reaction, meaning more product will be formed and there will be a lowering in the concentration of A through a reaction with B. This is particularly useful in industry or research where one of your reactants is expensive but the other is cheap - you can increase the yield of your reaction by increasing the concentration of your cheap reactant, pushing the position of equilibrium towards the products without having to increase the concentration of your expensive reactant. Similarly, decreasing the concentration of A would move the position of equilibrium towards the reactants to counteract this change and increase the concentration of A (meaning C + D would react to form A + 2B) The principle can also be used to see how changing the temperature of the reaction will affect the equilibrium position. If the forward reaction (A +2B ---> C + D) is exothermic (i.e. gives out heat, making the reaction mixture hotter), the backward reaction (C+ D ---> A + 2B) must be endothermic (i.e. absorbs heat decreasing the overall temperature of the reaction mixture). Thus, increasing the reaction mixture ourselves will push the position of equilibrium towards the left, allowing the system to absorb more heat and reducing the temperature of the system. Similarly, if all our reactants and products were gases, the side with more molecules on it would have a higher pressure than the side with fewer molecules (so in our example, 'A + 2B' would have the higher pressure, as there are 3 molecules on this side as opposed to only 2 on the 'C + D' side). Therefore, increasing the pressure would push the position of equilibrium towards the side with fewer molecules on it (in our case, the C + D side).  Decreasing the pressure would result in the opposite effect, with the position of equilibrium moving towards A + 2B to increase the pressure of the system!