Some translations set poetry farther to the right than the rest of the text to show that it is poetry. The ULB does this with the poetry in verses 9-13.
Kings and important people in John's time wrote important documents on large pieces of paper or animal skin. They then rolled them up and sealed them with wax so they would stay closed. Only the person to whom the document was written had the authority to open it by breaking the seal. In this chapter, "the one who was seated on the throne" had written the scroll. Only the person called "the Lion of the tribe of Judah, the Root of David" and "the Lamb" had the authority to open it. (See: [[rc://en/tw/dict/bible/other/scroll]] and [[rc://en/tw/dict/bible/kt/authority]])
Elders are church leaders. Twenty-four elders may be symbolic of the whole church through the ages. There were twelve tribes in Old Testament Israel and twelve apostles in the New Testament church. (See: [[rc://en/ta/man/jit/writing-apocalypticwriting]])
The "Lion of the tribe of Judah" and the "Root of David" are metaphors that refer to Jesus. Jesus descended from the tribe of Judah and the family of David. Lions are fierce, and all animals and people are afraid of them, so they are a metaphor for a king whom everyone obeys. The words "Root of David" speak of Israel's King David as if he were a seed that God had planted and of Jesus as if he were a root growing from that seed. (See: [[rc://en/ta/man/jit/figs-metaphor]])