You must have observed a young human baby. If you wave your hands in front of the eyes of a new born you will see that the child automatically closes her eyes. A human baby is born with simple reflexes and when grown as an adult the individual becomes capable of performing many complex behaviours. This happens because of learning.
The process of learning is continuous and goes on throughout life. From simple behaviours, like switching on the light, or picking up a book from the table to complex behaviours like driving a car or piloting a spaceship, all become reality only due to learning.
Learning empowers a person by making him or her what one is not and wants to become. All children are born with limited capacity of reflexes but it is only through learning that people become great scientists like Homi Bhabha, Vikram Sarabhai, leaders like Mahatma Gandhi and Pandit Nehru or any one whom you may admire. Without learning one is handicapped. People realize their potentials through learning and become what they dream.
Most of our behaviours are acquired through the process of learning. Learning may be defined as a relatively durable change in behaviour due to experience. Thus, if the change in behaviour is temporary, or due to instinct or maturation, it is not learning. The key feature of learning is experience. Any change in behavior in the absence of practice or experience does not qualify as learning.
For example the changes in the child, like crawling, standing and walking at certain ages are not included in learning. Similarly, illness and drug induced temporary changes are not due to learning. To qualify as learning, a change in behaviour must be relatively enduring.
Learning is not directly observable. It is often inferred from changes in the external behaviour. It is apparent in terms of improvement in the performance. You may recollect your own early childhood experiences when you were required to learn alphabets. In the beginning we make more errors. However, when we start practicing the errors decrease and a time comes when the behaviour becomes flawless. The decrease in the number of errors with increase in practice clearly indicates that learning is taking place.