Extracted from the excellent English(!) version of the Wikipedia article.
The five skandhas refes to the five aggregates of clinging, the five material and mental factors that take part in the rise of craving and clinging.
form
matter, body or “material form” of a being or any existence
sensation
sensory experience of an object. It is either pleasant, unpleasant or neutral.
perception
sensory and mental process that registers, recognizes and labels (for instance, the shape of a tree, color green, emotion of fear)
mental formations
types of mental imprints and conditioning triggered by an object. Includes any process that makes a person initiate action or act.
conciousness
awareness of an object and discrimination of its components and aspects.