Originally from South America, the potato is one of the most important basic foods. Most vitamins are contained in the skin. Nevertheless, it is not safe to eat potatoes raw, except in small amounts, since they contain the toxic alkaloid solanine. Green spots on the skin indicate areas of high concentration and should be cut out. Potatoes contain a varying amount of starch and certain varieties therefore work better for certain dishes.
From Wikipedia: “The potato is a starchy, tuberous crop from the perennial nightshade Solanum tuberosum. The word "potato" may refer either to the plant itself or to the edible tuber. In the Andes, where the species is indigenous, there are some other closely related cultivated potato species. Potatoes were introduced outside the Andes region approximately four centuries ago,and have since become an integral part of much of the world's food supply. It is the world's fourth-largest food crop, following maize, wheat, and rice.The green leaves and green skins of tubers exposed to the light are toxic.”
“While there are close to 4,000 varieties of potato, it has been bred into many standard or well-known varieties, each of which has particular agricultural or culinary attributes. In general, varieties are categorized into a few main groups, such as russets, reds, whites, yellows (also called Yukons) and purples—based on common characteristics. Around 80 varieties are commercially available in the UK. For culinary purposes, varieties are often differentiated by their waxiness. Floury, or mealy (baking) potatoes have more starch (20–22%) than waxy (boiling) potatoes (16–18%).”
More information about cooking types:
Waxy potatoes, also called firm-boiling potatoes work well to make fried potatoes, gratins, and potato salad because they hold together well. Round white and yellow potatoes fall into this category as do new potatoes.
Starchy potatoes are ideal for mashed potatoes and casseroles as they don’t hold their shape well. Russets and Idaho potatoes are in this category.
All-purpose potatoes are used to make dishes such as boiled potatoes, fried potatoes, and soup. The starch content is in between that of waxy and starchy potatoes. Yukon Gold potatoes are in this category.
“The potato contains vitamins and minerals, as well as an assortment of phytochemicals, such as carotenoids and natural phenols. Chlorogenic acid constitutes up to 90% of the potato tuber natural phenols. Others found in potatoes are 4-O-caffeoylquinic acid (crypto-chlorogenic acid), 5-O-caffeoylquinic (neo-chlorogenic acid), 3,4-dicaffeoylquinic and 3,5-dicaffeoylquinic acids. A medium-size 150 g (5.3 oz) potato with the skin provides 27 mg of vitamin C, 620 mg of potassium, 0.2 mg vitamin B6 and trace amounts of thiamin, riboflavin, folate, niacin, magnesium, phosphorus, iron, and zinc.
The potato is best known for its carbohydrate content (approximately 26 grams in a medium potato). The predominant form of this carbohydrate is starch. A small but significant portion of this starch is resistant to digestion by enzymes in the stomach and small intestine, and so reaches the large intestine essentially intact. This resistant starch is considered to have similar physiological effects and health benefits as fiber: It provides bulk, offers protection against colon cancer, improves glucose tolerance and "insulinsensitivity", lowers plasma cholesterol and triglyceride concentrations, increases satiety, and possibly even reduces fat storage. The amount of resistant starch in potatoes depends much on preparation methods. Cooking and then cooling potatoes significantly increases resistant starch. For example, cooked potato starch contains about 7% resistant starch, which increases to about 13% upon cooling. The storage and cooking method used can significantly affect the nutrient availability of the potato. Potatoes are often broadly classified as high on the glycemic index (GI) and so are often excluded from the diets of individuals trying to follow a low-GI diet.”
“The English word potato comes from Spanish patata (the name used in Spain). The Spanish Royal Academy says the Spanish word is a compound of the Taíno batata and the Quechua papa (potato).”