People in the Paleolithic age got food by hunting and gathering Animals and other things. Some problems are that people have are that hunting was dangerous, and animals would become scarce if the people stayed put for too long.
We learned that we could grow our own food. This is possible by collecting and planting the seeds of plants.
We learned that when we domesticated animals, we could tell them what to do. Domesticated animals can get things for us, carry items, transportation, etc.
The invention of agriculture is important because we would have some sort control over our food supply.
The growth of trade allowed people to make use of more resources and contact with people from distant places. These contacts spread ideas and knowledge throughout the ancient world.