Agave syrup is the cooked down juice of the agave, a genus of spiny, perennial plants native to Mexico. It is a more reduced, thicker and sweeter version of agave nectar. Agave syrup is moderately sweet, and can be used in place of honey.
Agave nectar is not as sweet as honey, with a delicate, floral-vegetal overtone. It lacks the midpalate breadth that honey has, and has a short finish so that it seems more transparent. It can be substituted easily for simple syrup in most applications.