When of good quality, apples can be eaten raw with or without the peel. However, there are many valuable nutrients in the peel that you don’t want to miss out on.
From Wikipedia: “The apple tree (Malus pumila, commonly and erroneously called Malus domestica) is a deciduous tree in the rose family best known for its sweet, pomaceous fruit, the apple. It is cultivated worldwide as a fruit tree, and is the most widely grown species in the genus Malus. The tree originated in Central Asia, where its wild ancestor, Malus sieversii, is still found today. Apples have been grown for thousands of years in Asia and Europe, and were brought to North America by European colonists. Apples have religious and mythological significance in many cultures, including Norse, Greek and European Christian traditions. ...
There are more than 7,500 known cultivars of apples, resulting in a range of desired characteristics. Different cultivars are bred for various tastes and uses, including cooking, eating raw and cider production. Trees and fruit are prone to a number of fungal, bacterial and pest problems, which can be controlled by a number of organic and non-organic means.”
“Apples are often eaten raw. The whole fruit including the skin is suitable for human consumption except for the seeds, which may affect some consumers. The core is often not eaten and is discarded. Cultivars bred for raw consumption are termed dessert or table apples.
Apples can be canned or juiced. They are milled or pressed to produce apple juice, which may be drunk unfiltered (called apple cider in North America), or filtered. The juice can be fermented to make cider (called hard cider in North America), ciderkin, and vinegar. Through distillation, various alcoholic beverages can be produced, such as applejack, Calvados, and apfelwein. Apple seed oil and pectin may also be produced.”
“Apples are an important ingredient in many desserts, such as apple pie, apple crumble, apple crisp and apple cake. They are often eaten baked or stewed, and they can also be dried and eaten or reconstituted (soaked in water, alcohol or some other liquid) for later use. When cooked, some apple cultivars easily form a puree known as apple sauce. Apples are also made into apple butter and apple jelly. They are also used (cooked) in meat dishes.
Sliced apples turn brown with exposure to air due to the conversion of natural phenolic substances into melanin upon exposure to oxygen. Different cultivars vary in their propensity to brown after slicing and the genetically engineered Arctic Apples do not brown. Sliced fruit can be treated with acidulated water to prevent this effect. Sliced apple consumption tripled in the US from 2004 to 2014 to 500 million apples annually due to its convenience.”
“Organic apples are commonly produced in the United States. Due to infestations by key insects and diseases, organic production is difficult in Europe. The use of pesticides containing chemicals, such as sulfur, copper, microorganisms, viruses, clay powders, or plant extracts (pyrethrum, neem) has been approved by the EU Organic Standing Committee to improve organic yield and quality. A light coating of kaolin, which forms a physical barrier to some pests, also may help prevent apple sun scalding.”
Toxicity of seeds:
“The seeds of apples contain small amounts of amygdalin, a sugar and cyanide compound known as a cyanogenic glycoside. Ingesting small amounts of apple seeds will cause no ill effects, but consumption of extremely large doses can cause adverse reactions. It may take several hours before the poison takes effect, as cyanogenic glycosides must be hydrolyzed before the cyanide ion is released.”
“Apple trees are large if grown from seed. Generally apple cultivars are propagated by grafting onto rootstocks, which control the size of the resulting tree.”