Gelatin is a mixture of peptides and proteins produced by partial hydrolysis of collagen extracted or taken from the skin, bones, and connective tissues of animals such as domesticated cattle, chicken, pigs, and crab fish. 

Photographic and pharma grades of gelatin are generally made from beef bones, although some beef bone gelatin is used by the food industry. 

Gelatin is an animal protein unlike many other gelling agents used by the food industry.

It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. 
Substances containing gelatin or functioning in a similar way are called gelatinous.

It is found in most gummy candies as well as other products such as marshmallows, gelatin dessert, and some ice cream, dip and yogurt. 

Gelatin is an irreversibly hydrolysed form of collagen, and is classified as a foodstuff. 

Household gelatin comes in the form of sheets, granules, or powder. 

Instant types can be added to the food as they are; others need to be soaked in water beforehand.
Here are some of the food products which contains gelatin. click to see the images and to read