to whom is the Lord Jesus speaking? what does a lampstand signify?
The lampstands, or as the KJV states it, the candlesticks of Rev 2:5, represented the corporate churches, not the eternal heavenly or true church. The earthly candlestick was made by Moses at the direction of God, and therefore, was an example/depiction of the true. The true candlestick however is in heaven and is eternal as-is, having been built by God Himself. The man-made candlestick on the other hand, was intended only as a mirror of the true, but was not the true itself, as all of its congregants were not always of the true, and thereby were both corporately subject to committing the spiritual sins of man. However, from God's perspective, not so with the heavenly. With the heavenly, it, being the eternal one, as are its congregants of the eternal, will not/cannot be removed from their place because they are there by Christ, not of themselves. Those who are elected to salvation- the saved - alone are its eternal congregants. Consequently, when the leadership of an earthly candlestick (church) - which church was a physical manifestation of Moses's candlestick - went astray from the truth of Christ, and thereby led his church astray, God reserved and executed the right to remove that candlestick (that earthly church) from its place and from remaining as His and heaven's earthly representation/representative. The warning given to those churches were directed to the saved congregants within it, that they should replace the leadership (or whoever had led it astray) and make the needed corrections so that only the true gospel would henceforth be preached by it. Unfortunately, not all of those churches over time heeded that warning.
Nevertheless, the saved of that church, eternally would/will retain in their place in the heavenly candlestick as being its congregants.
There is great distinction yet to be made and examined between the heavenly candlesticks and the earthly candlesticks, but this thread is probably not the appropriate place for doing so.
The candlestick was part of, and within, the tabernacle.
[Exo 25:9 KJV]
9
According to all that I shew thee, [after]
the pattern of the tabernacle, and the pattern of all the instruments thereof, even so shall ye make [it].
[Exo 25:31 KJV]
31
And thou shalt make a candlestick [of] pure gold: [of] beaten work shall the candlestick be made: his shaft, and his branches, his bowls, his knops, and his flowers, shall be of the same.
[Psa 1:4-5 KJV]
4 The
ungodly [are] not so: but [are] like the chaff which the wind driveth away.
5 Therefore the ungodly shall not stand in the judgment,
nor sinners in the congregation of the righteous.
[Heb 8:2 KJV]
2 A minister of the sanctuary, and of
the true tabernacle,
which the Lord pitched, and not man.
[Heb 8:5 KJV]
5
Who serve unto the example and shadow of heavenly things, as
Moses was admonished of God when he was about to make the tabernacle: for,
See, saith he, [that] thou make all things according to the pattern shewed to thee in the mount.