Learning, as the noun, is the body of knowledge and wisdom (that which one learns); as the verb, it is the process of gaining understanding that leads to the modification of attitudes and behaviors through the acquisition of knowledge, skills and values, through study and experience.
Learning induces a persistent, measurable, and specified behavioral change in the learner to formulate a new mental construct or revise a prior mental construct. The learning process leads to long-term changes in behavior potential. Behavior potential describes an individuals possible behavior in a given situation to achieve a goal. But potential is not enough; if individual learning is not periodically reinforced, it becomes shallower and shallower, and eventually will be lost in that individual. 
Sources: Wikipedia.org