I think you might find it helpful to read the whole of Revelation 4. It begins with a door (Jesus calls Himself the Door, in John 10:6 - 9.) being opened in heaven and what John (the apostle) could see there. This is mainly a picture of worship, and cries of 'Holy, holy, holy' to the Lord God Almighty. Is this any clearer now?Worthy is the lambJesus Christ is the Lamb (who was slain), as announced by John the Baptist at the beginning of (the disciple) John's gospel.John 128 These things were done in Bethabara beyond Jordan, where John was baptizing. 29 The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world. 30 This is he of whom I said, After me cometh a man which is preferred before me: for he was before me. 31 And I knew him not: but that he should be made manifest to Israel, therefore am I come baptizing with water. 32 And John bare record, saying, I saw the Spirit descending from heaven like a dove, and it abode upon him. 33 And I knew him not: but he that sent me to baptize with water, the same said unto me, Upon whom thou shalt see the Spirit descending, and remaining on him, the same is he which baptizeth with the Holy Ghost. 34 And I saw, and bare record that this is the Son of God. 35 Again the next day after John stood, and two of his disciples; 36 And looking upon Jesus as he walked, he saith, Behold the Lamb of God! 37 And the two disciples heard him speak, and they followed Jesus.