At the most simple level, learning is accepting the fact that two events in the world coincide in timely manner. It is also how children learn about the world by connecting something they do like seeing a ball throw down and bounce or even connecting their behavior to a parents reaction.
To simplify: our brain is making rules, you have a first event that is immediately followed a second event.
In the brain every time we learn something we don’t gain new neurons, but rather we change the connections between neurons.
In the brain we used the term “plasticity”, to refer to this idea that the brain is not fixed or set. It can be changed based on certain events.
Learning is thought to occur between neurons. When a neuron is “activated” it sends an action potential or a burst of electricity down its axons which may extend far away from its body. At the tail end of the axon, the cell releases vesicles of neurotransmitters. These neurotransmitters are received by nearby cells though a “synapse”, literally the space between the cells. The cell at the receiving end is receptive to the neurotransmitters if it is has a receptor for the neurotransmitter released. If the receptor exists then that cell itself will fire. If this repeatedly happens that these cells fire one after another then the receiving cells will over time create more receptors on its surface. With this new ability to catch more neurotransmitters then the cell will fire more and more frequently so that they are firing together. Their relationship has been strengthened.
A new event has been learned. Or according to Donald Hebb, “Cells that fire together, wire together.”