The Full Achievement

The Helmet denotes the rank of the bearer (see Helmets for a more indepth discussion of that).
The Crest, which is sometimes used to (incorrectly) refer to the entire achievement,is actually, either a crest wreath (consisting of a twisted parti-coloured material - usually the first metal and first tincture of the blazon) or a crest coronet, and from either of those, would arise the crest itself. A bit confusing, I'll admit.
The Mantling flows from the helmet, and is "held in place" by the crest - it is depicted as a cut and shaped cape - usually coloured with a tincture on the outside, and a metal or fur on the inside. The Mantling was thought to shade the knight, or protect his neck from blows.
Not all achievements were awarded with Supporters - usually only those of peers (Knights, and titled persons). The supporters could be af many different fanciful forms, both creatures, and humans were popularly used. Most times, people were coloured naturally, but creatures (including those in the crest) were often coloured according to the overall colour scheme of the achievement, including, on occasion, even parti-colouring!