A feature is DrawShield specific term for part of a charge that can be given a different colour from the main body. For example, in the phrase a lion or armed and langued gules there are two features, armed (i.e. claws) and langued (the tongue), both of which are coloured red.
There are many hundreds of features that are recognised by the program. many of which are specific to only a small number of charges, however there are some features that are common to larger groups.
Common Bird and Animal Features
Armed, langued, unguled, legged, beaked, muzzled, crowned, attired, horned
Common Weapon Features
Shafted, heads, handled, feathered, points, blades, pomells
Common Flower Features
Slipped, leaved, trunked, fructed, seeded, barbed
This is only a subset of the possible features, and as usual the quickest way to find out whether a specific feature is recognised is to try it out in the "Create" page.