What does dogen's genjo-koan mean?

What does the genjo-koan means? Especially: > To study the buddha way is to study the self. To study the self is to > forget the self. To forget the self is to be actualized by myriad > things. When actualized by myriad things, your body and mind as well > as the bodies and minds of others drop away. No trace of realization > remains, and this no-trace continues endlessly. and > A fish swims in the ocean, and no matter how far it swims there is no > end to the water. A bird flies in the sky, and no matter how far it > flies there is no end to the air. However, the fish and the bird have > never left their elements. When their activity is large their field is > large. When their need is small their field is small. Thus, each of > them totally covers its full range, and each of them totally > experiences its realm. If the bird leaves the air it will die at once. > If the fish leaves the water it will die at once. > > Know that water is life and air is life. The bird is life and the fish > is life. Life must be the bird and life must be the fish. > > It is possible to illustrate this with more analogies. Practice, enlightenment, and people are like thi What does it mean to say that these are life and that there's no realisation?