4:4 And around the throne were twenty-four thrones; and upon the thrones I saw twenty-four elders sitting, clothed in white garments, and golden crowns on their heads.

And AROUND THE THRONE were 24 thrones; and upon the thrones I saw 24 elders

The identity of the 24 elders is much debated. In 1 Chronicles 23:3-5, David assigned 24,000 Levites to do the work in the house of the Lord. In 1 Chronicles 24:3-5, of the priests, there were 24 "chief men" (16 from Eleazar; 8 from Ithamar). Perhaps, heaven is organized the same way.

Now "sitting" may mean witnesses to the judgment to take place NOT as a jury but like when an execution takes place to 'validate' it. These 24 elders do also fall down before the One on the THRONE and cast their crowns before the One (verse 10). Thus these are not statues but live beings.

The "WHITE GARMENTS" denote purity and righteousness. These elders are 'clean' before God. If these garments have been washed, then they are redeemed by Christ's blood (Sardius).

The golden crowns are promised rewards to believers, in particular, those at the church in Smyrna (Revelation 2:10). All believers who love his appearing will receive the crown of righteousness (2 Timothy 4:7-8).

Later on in Revelation 5:8, we find the elders also have a harp and golden bowls of incense. The harps make sweet music to worship the Lord. The golden bowls contain the prayers of the saints. The 24 elders have been cleansed such that they can approach the main THRONE of God. Halelujah!

A little sidelight, the 4 living creatures also are associated with the 24 elders. The significance of this is not known.