Resveratrol is  found in red grape skins and grape seeds and into some extent in peanuts.

Resveratrol is also found in some  other plants- for example- Japanese knotweed [ Polygonum cuspidatum] which is also the source of some supplements.

Resveratrol exists in chemically either the cis- or trans- form.

In nature, the trans- form is most abundant. It is also the form most used in supplements.

 Pinot Noir red wine has the highest level of resveratrol of the various wine products.

 Clinical studies found that resveratrol significantly improves blood sugar and insulin sensitivity in  diabetics.

Resveratrol has become famous as a possible  life-extendingsupplementt.[ this was shown in experiements in mice who were fattened]

The claim that Resveratrol extends life maybe was exaggerated [?], as this benefit may be limited to those with type 2 diabetes 

Other experiments with animals have shown positive effects on colitis and heartfunction as well as anti-inflammatory anticancer and antiplatelet effects [less chanche of thrombosis] as well as improving cholesterol levels.

As resveratrol is a very concentrated supplement is is wise to discuss long term use with your physician.

In the coming years likely much more will become known /confirmed.