From Anstey’s Doctrinal Definitions:
This refers to the irrevocable damnation of people who pass out of this world in their sins. It applies to Satan and his angels as well.
Many think that judgment and condemnation are the same thing, and use the terms interchangeably. However, this is not true. “Judgment” is the sentence or verdict that has been passed upon all men because all have sinned. (Some Bible versions translate "judgment" as "verdict" to indicate this.) If men come to Christ and get saved, they avert this judgment. “Condemnation,” on the other hand, is a final and irrevocable thing; it is never reversed. It is the future portion of all who pass out of this world in their sins without faith (Mark 16:16 – "shall be condemned"). "The world" (1 Cor. 11:32), "the flesh" (Rom. 8:3), "the devil" (1 Tim. 3:6), and people who have died in their sins (John 5:29) are the only things and persons that are said to be under condemnation now. Hence, men who are alive in this world in their sins are under judgment, but they are not under condemnation—at least not yet. If they pass out of this world in their lost condition, they will then pass into condemnation.
Romans 5:16 shows clearly that judgment and condemnation are not synonymous. It says, "The judgment was by one unto condemnation." This shows that judgment precedes condemnation. W. Scott said, "Judgment and condemnation do not mean the same thing. Condemnation is future and final. Judgment precedes it." J. N. Darby states in the footnote of his translation in Luke 20:47 that the word "judgment" is "the sentence passed on the thing charged as guilt; the charge itself is the ground of judgment, not the fact of condemnation."
Some might wonder how John 3:18 fits with this. It says, "He that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God." However, this is a mistranslation in the KJV. It should read, "judged," rather than condemned. Romans 8:1 states, "There is therefore now no condemnation to them which are in Christ." Note: it does not say, as some imagine, "There is now no more condemnation to them which are in Christ"—which would imply that they were once under condemnation, but they have escaped it through faith in Christ. The point in the verse is that, resulting from being justified and being "in Christ," it is impossible for the believer to ever come into "condemnation."
C. H. Mackintosh said, "The English reader should be informed that, in the entire passage, John 5:22-26, the words "judgment," "condemnation," and "damnation" are all expressed by the same word in the original, and that word is simply "judgment"—the process, not the result." (Papers on the Lord's Coming, p. 48).
J. N. Darby said, "We all know, if we know anything, the difference between past sins (or present) and the evil nature [sin]; the fruit; and the tree. If it is asked, 'Is a man condemned for both?' I should say, that he is lost, rather than condemned" (Collected Writings, vol. 34, p. 406).