Hormones are signaling molecules that conveys information from one point to another, typically through a soluble medium like the extracellular fluid or blood.
Hormones fall into one of a number of different hormonal classes eg, steroids, monoamines, peptides, proteins, and eicosanoids.
They signal through a variety of general (eg, nuclear vs cell surface) and specific (eg, tyrosine kinase vs phosphoinositide turnover) mechanisms in target cells.