When the S&P 500 rises 54 points, those points came from somewhere: every one of them is attributable to specific stocks. Point contribution is the accounting that does it. A stock's contribution is the number of index points its own move added or subtracted, so the contributions of all members sum exactly to the index move. If Nvidia contributed 12 points of a 54-point gain, that is not a metaphor; remove Nvidia's move and, holding everything else fixed, the index rises 42.
How a stock's move becomes points depends on how the index is built. In a cap-weighted index like the S&P 500 or the Nasdaq-100, contribution is roughly the index level times the stock's weight times its return: size is leverage, so a 1% move in a 7% weight moves the index far more than a 10% move in a 0.05% weight. In the price-weighted Dow, every dollar of price change contributes the same number of points regardless of company size, which is why a high-priced share can dominate the Dow while barely registering in the S&P.
Points are a better unit than percentages for explaining a session because they are additive. Percent returns of members cannot be summed into the index return without the weights; points can, and the arithmetic must close. That closure is also a truth check: WMTMT reconstructs each index from its members' prices and verifies the sum against the official close before publishing anything, with the residual disclosed.
Every day's market-close note shows the full decomposition: who contributed which points, top to bottom.