The coat of plates is a type of body armor comprised of overlapping plates riveted mainly to the inside of either a leather or fabric shell but sometimes also attached to the outside is the staple of 14th century body armor. This type of armor was low cost to produce and still is and was used throughout the entire century, which is something to be said considering the constant flux of armor in this century.
Chainmaille was also used throughout the century but started at nearly knee length with long sleeves and mufflers (mittens) and shortened to that similar to a modern day t-shirt. It was worn under virtually any other type of body armor and sometimes overtop.
By 1340 the breastplate came into existence in the form of a short plate defence covering the upper chest. This developed into the full breastplate we now associate with a knight in shining armor including a fauld (skirt made of overlapping horizontal bands) by 1370.
The brigandine also came into being during the 14th century by around 1370. Similar to the coat of plates a brigandine was comprised of much smaller overlapping plates with larger plates to cover the lungs and heart attached to the inside of a canvas shell usually covered in a fine material such as silk velvet.