Q.(-)CH2-C(=O)-CH3 and CH2=C(-O^-)-CH3 (structures shown in the original paper) are:

Resonance structures (canonical forms) represent the same molecule/ion with the same arrangement of atoms and same connectivity, differing only in how the electrons (and formal/negative charge) are distributed — exactly what the two given structures show for the enolate anion of acetone.

The two structures given are:

(1) (-)CH2-C(=O)-CH3 — the carbanion form, with the negative charge localised on the terminal CH2 carbon and a C=O double bond to the middle carbon.

(2) CH2=C(-O^-)-CH3 — the enolate form, with a C=C double bond between the same two carbons and the negative charge now on the oxygen.

In both structures, the positions of every atom (the three carbons, the oxygen, and all hydrogens) are exactly the same — only the arrangement of the pi electrons and the location of the formal negative charge differ (delocalised between the carbanion carbon and the oxygen). This delocalisation of electron density over a fixed framework of atoms is precisely what defines resonance (canonical) structures — they are not two different, isolable compounds, but two ways of drawing the same real hybrid species.

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