Entropy measures the amount of disorder in a system. Nature tends towards disorder, so as time elapses, entropy naturally increases. Energy is required in order to decrease entropy.
Entropy, when I think of entropy I think of my four year old daughter, if she comes into her room no matter how clean it is, pretty soon it's chaos and disorder and we've got to go in there and kind of fix everything up and kind of straighten it out so basically entropy is the amount of disorder within a system.
So let's look at an example of entropy, let's say I've got water and I've got that water frozen in a nice little ice cube okay and this ice cube has a lot of order and a lot of structure and all these molecules are held together in these very tight precise bonds okay, now if we let that ice cube melt, it's going to gain entropy it's starting to gain energy and it's starting to move around and it's losing that order and that structure it's moving towards disorder and so now our ice cube, I'm going to put it in a little cup, is going to become water with more energy and more motion and more disorder. If we let that continue to evaporate, it's going to turn into water vapor and it's going to become all the molecules in air in water vapor and that's got a lot of energy and a lot of disorder and those molecules are going everywhere and bouncing and colliding in to other things, so that is the a system with a lot of disorder high entropy. But as the water is going from order to disorder that energy is also causing an increase in entropy in the air molecules around it as the ice is melting the air around it is, is getting cooler and that's causing a decrease in Entropy and as water evaporates, that evaporate of cooling is cooling off the air which causes a decrease in entropy in the air so entropy can go in two directions and often times it goes in two complimentary directions as one thing heats up and another cools off.