Paradise was the place of departed spirits. The bosom of Abraham was where the children of Israel went until the Messiah came to claim them. Christ told the thief that he would be with Him in Paradise and that was so, then Jesus cleaned out the Bosom of Abraham and took them with Him.
Nice succinct explanation.
I thought the article was pretty straightforward.
This assumes a Dichotomous anthropology of man, whereas the New Testament speaks of a Trichotomous anthropology of Adam and the Second Adam, i.e., body, soul, and spirit, vice body and soul/spirit.
Note we do not receive the human spirit regenerated until we exercise faith in Christ. Nor can any man understand things spiritual until he receives the human spirit when he is born again, because they are spiritual (something void to him, until the 2nd birth).