The Anthropic principle is a relatively simple idea. It states that we see the universe the way it is because if it were different, there would be no one here to observe it. This principle is not very predictive. It is opposed to the principle that states that nature's laws are the way they are and the universe is the way it is because it would not be possible any other way. To think of it in an easier way, this principle states that the universe cannot be something other than what we observe because if it were, we would not exist and therefore be incapable of observing it.
The Anthropic Principle has two versions to it, the weak and the strong. The weak version states this: that in an infinitely large or just very large universe, only certain regions throughout space and time will evolve enough to support any kind of intelligent life. The creatures that inhabit these regions are therefore not amazed if the region they live in is suitable to them and support life as a whole. For example, it is like a pauper living in a poor, shunned neighborhood and not seeing or knowing what wealth is. This person just sees that the environment surrounding him must be suitable to support him because if it weren't, he would not exist.
The Strong Anthropic Principle states that either in many universes or in one universe with many regions, there are many possibilities and configurations within them, with their own laws of science and nature that decide whether life in these regions or universes is possible. The places where life is possible, life will arise and according to this principle, we are in one of those regions or universes because if we were not, we wouldn't exist.