16 Also it causes all, both small and great, both rich and poor, both free and slave, to be marked on the right hand or the forehead, 17 so that no one can buy or sell who does not have the mark, that is, the name of the beast or the number of its name.
I want to recap all the things that John of Patmos prophesies will happen before the mark of the beast is given. First, either the last verse of Revelation 12 or the first verse of this chapter depending on the translation, says "the dragon took his stand on the land of the seashore". Then a beast of arises out of the sea drawing his power from the dragon, which most writers believe symbolizes Satan/the devil. This beast has ten horns and seven heads, and wears ten crowns, or diadems. One of his heads has incurred a mortal wound, which was miraculously healed. In verse four of this chapter we are told the whole world worships this beast from the sea, that has been given power by the 'dragon' which represents Satan.
This beast is haughty and arrogant and blasphemes God, and makes war on the saints, and all non-Christians will worship it, according to verses five through eight.
Then arises a second beast, coming out of the earth, having horns like a lamb (like Christ) but the voice of a dragon (symbolizing Satan). This second beast exercises the authority of the first one, the beast from the sea, and forces every human being to worship the first beast. Many writers interpret these beasts to be a military leader and a false prophet working together. This beast causes people to be marked on their right hand or forehead as a symbol of their worship of this false Christ. But even before the mark is taken, in verse fifteen we are told that all those who refuse to worship an image of this beast are murdered for not doing so.
Because of the language used in verse sixteen some scholars interpret this to mean a mark that is not literal, but that is given upon their being because of their worship of the false Christ. Traditionally though, Christians have been taught that this verse refers to an actual physical mark one must be given to qualify one to buy or sell in the society governed by this world leader that slaughters everyone that won't bow to his image.
The writer at Crossway.org says the first beast represents Rome, but also likens the symbolism of seven heads and ten horns to all governments that are tyrannical or authoritarian.
At the gotquestions.org entry on this passage, the writer speculates on how this mark might manifest, such as an RFID chip or tattooed bar code or something of that nature. Importantly, this author also drives home the point that the Anti-christ will be revealed before the mark is given. There does not appear to be any such figure on the world stage at this point, which is why it is disturbing that so many people want to contort the meaning of this chapter and claim the Covid vaccine is somehow the 'mark of the beast'.
I believe we are given these warnings in Revelation so that we can watch and wait for these 'beast' figures, empowered by Satan, and guard against worship of the beast and taking even a figurative or literal mark of worship of the beast, an idolatry that many writers believe is closely associated with money and greed. I hope everyone will accept Salvation from Christ and receive the bread of Salvation, the only true redemption for our souls in this world of greed and warfare.
A Prayer for Salvation from Christ:
Lord Jesus, I confess my sins and ask for your forgiveness. Please come into my heart as my Lord and Savior. Take complete control of my life and help me to walk in Your footsteps daily by the power of the Holy Spirit. Thank you Lord for saving me and for answering my prayer.
A more detailed step by step process:
https://www.wikihow.com/Accept-Jesus-Into-Your-Life