Learning is a blanket term that covers a broad spectrum of activities that leads to the acquisition of skills and knowledge. People can learn deliberately through observation, direct instruction, physical activities, reading, and listening. These are known as "active" learning.
"Passive" learning, on the other hand, is the trial and error process that we all use every day to find out what works and what doesn't and the most efficient ways of accomplishing tasks. Pyschologists study "learning" to better understand how and why different methods work for different people. These are called learning "styles."
Psychologists also study the existence of learning disabilities, or why some people have extra difficulties learning things that other find easy.