The term “throne” is common in the book of Revelation, particularly to denote the sovereignty of God (Revelation 4:2; Revelation 5:1; Revelation 12:5). In the present verse John sees multiple thrones (we are not told how many). As a “throne” represents authority, we need to know that in some way God has shared his authority with those seated on them (see also Revelation 4:4), namely, “those to whom the authority to judge was committed.”
4 Then I saw thrones, and seated on them were those to whom the authority to judge was committed. Also I saw the souls of those who had been beheaded for the testimony of Jesus and for the word of God, and those who had not worshiped the beast or its image and had not received its mark on their foreheads or their hands. They came to life and reigned with Christ for a thousand years.