Borateem
Contained various other additives over the product's long history besides borax. Surfactants, antibacterial agents, bluing/OBA and so forth.
Borax has (very) mild disinfecting and antimicrobial properties along with releasing small amounts of oxygen in water. Hence sodium perborate is combining hydrogen peroxide with borax.
Compared to washing soda, sodium metasilicate and other salts borax is rather mild; thus not likely to harm most fabrics or colors. It has long been used on wash day for delicates, baby's things, and other laundry you wouldn't want harshly treated.
That being said like adding 1/4 cup or less of borax to wash loads when using liquid detergents and not any sort of oxygen bleach. Especially for dress shirts as it helps take out whiffy smells, including underarm.