What does Revelation 4:9 mean?

Before the throne was something like a sea of glass, similar to crystal. In the middle of the throne, and around the throne were four living creatures full of eyes before and behind.

The first creature was like a lion, and the second creature like a calf, and the third creature had a face like a man, and the fourth was like a flying eagle.

The four living creatures, each one of them having six wings, are full of eyes around and within. They have no rest day and night, saying, “Holy, holy, holy is the Lord God, the Almighty, who was and who is and who is to come!”

the twenty-four elders fall down before him who sits on the throne, and worship him who lives forever and ever, and throw their crowns before the throne, saying,

“Worthy are you, our Lord and God, the Holy One, to receive the glory, the honor, and the power, for you created all things, and because of your desire they existed, and were created!”