These versions are designed for embedding on web sites. To keep them as small as possible, they lack many of the symbols found in the Print/PDF versions. The WOFF versions are unhinted, because it makes a big difference to file size. Use ttfautohint to add hinting if you need it.

They contain many OpenType features, including Alternative Fractions (Stacking-fractions), Petite and Small Capitals from Capitals, Petite and Small Capitals, Capital Spacing, Character Variants,  Discretionary Ligatures, Historical Ligatures, Standard Ligatures, Superscripts, Subscripts, Scientific Inferiors, Ordinals, OldStyle Figures, Fractions, Ornaments, Stylistic Sets, Stylistic Alternates, Slashed Zero, and Kerning.

The WOFF (Web Open Font Format) versions are compressed. The disadvantage is that they cannot be installed in Windows and cannot be embedded automatically using Serif WebPlus X8.  You will need to add suitable @FontFace code manually to make use of them.