Active transport is the movement of molecules from an area of low concentration to an area of high concentration, against the concentration gradient.

Therefore this requires the input of energy from the cell.  

Scroll over the protein channel

Carrier proteins move these molecules through the plasma membrane against the concentration gradient.

In humans, we can see active transport during digestion.

Carbohydrates are broken down into simple sugars such as glucose.

The glucose is absorbed through active transport into the villi and passed into the bloodstream.