What are "Cheivan/"?
Rashi: They are Chayos.
What is the significance of Ruchos and Chayos?
Malbim: Ruchos represent powers of supreme Sarim that influence on nations. They stand on the four directions of the Merkavah. Yechezkel saw them in the form of Chayos. Daniel saw the Chayos that develop from them in ruling over the lower world.
What is the significance of the Chayos being big?
Malbim: There are also small Chayos, i.e. small kingdoms. The big Chayos grow bigger than them, and come out of the sea to rule over the entire world.
What is the significance of the Chayos being different than each other?
Malbim: Each kingdom has a different conduct and nature.
