What it means
Pairs such as AV or To can create awkward spaces even when each character has reasonable side bearings. A font can include pair adjustments that a browser applies during shaping. Kerning is different from tracking, which changes spacing across a whole run of text.
Use it in practice
Inspect prominent words at their final size, especially short logos or large headlines. Let the font do the routine work before considering manual adjustments.
Watch out for
Do not fix one awkward pair by spreading every letter in the headline. Avoid drawing conclusions from a sample rendered at a different size.
