This is the green paste looking stuff you will find in the head. Technically it serves as a combination liver and pancreas. It looks somewhat like wasabi paste and often used in sauces.
Right under the body shell are the spongy, feathery gills wrapping around the outside of the body cavity.
The eggs are called roe and are bright orange after cooking. They can be found in the tail and the body cavity.
Those skinny things they walk on.
All that other stuff under the shell