Felodipine is an example of a calcium channel blocker. It works by relaxing and widening the blood vessels which transport blood around the body:

Felodipine blocks the calcium which enters the cells (the building blocks of the body) that make up the muscles in the heart and blood vessels.
Calcium is vital for muscles to contract so if it is blocked the muscles are automatically relaxed.
The relaxing of these muscles makes it easier for the heart to pump blood around the body and so blood pressure is lowered.