Source: http://www.nhlbi.nih.gov/health/dci/images/stent_lowres.gif

Stent is an implantable cardiovascular device which is used to open a blocked blood vessel. In the above figure, it is shown as it is been deployed in the coronary artery, during a balloon angioplasty procedure.

A variation of the stent is 'drug eluting stent', such as the 'Boston Scientific Taxus Express' . Structurally it is same as the conventional stent. However the stent has a surface coating that makes it more non-thrombogenic.