What are the differences between a dinosaur skeleton and an insect encased in amber?

Assuming you meant a dinosaur fossil and an insect fossilized in amber, the difference is that the soft tissues of the insect remain whereas the dinosaur fossil shows only hard tissues such as bone and tooth. Additionally, the insect fossil is the actual insect, wheras the dinosaur fossil is a stone formation that was created by rock replacing the bones of the dinosaur.