tabular-nums aligns digits by width

In a few sentences

In brief

The same width of numbers makes it easy to scan numbers in a column.

Useful to know

font-variant-numeric: tabular-nums includes tabular digits when the font supports them. Each digit occupies an equal width, which is convenient for clocks, counters, and number tables. [1]

Example: .amount { font-variant-numeric: tabular-nums; }. This does not automatically align the decimal separator and does not format the currency. For comparable amounts, uniform rules for recording and appropriate alignment of cells are also needed. If the font file does not have the corresponding variants, the expected change may not appear. Check the actual figures, not just the CSS declaration.

Sources

For further detail and to check the information:

[1] MDN — font-variant-numeric ↗