What is involved in active transport?

This question comes up often in GCSE papers and is a key topic when talking about exchange or cell biology. 
Active transport comes hand in hand with diffusion and osmosis. It is a key mechanism for moving substances, usually small molecules, into, out of, or between cells.
Active transport is required when we want to move substances against a concentration gradient. Active transport is so called because it requires energy. This energy used in active transport is provided by respiration.
Active transport is used in root hairs for absorbing minerals out of the soil (from a low to high concentration).It is used in digestion when there is a lower concentration of nutrients in the gut, and a higher concentration in the bloodstream.
Answering the question: What is active transport? 
1) Active transport is the net movement of molecules......
2) from an area of low concentration to high concentration/against the concentration gradient..
3)....and requires energy from respiration.
For a long answer exam question, think about where active transport is involved, e.g. in root hairs active transport moves minerals from a dilute concentration, against a concentration gradient, from the soil and into the plant.