Guava is a plant of the myrtle family scientifically known as Myrtaceae. It is represented by the genus psydium with 100 known species of tropical shrubs and small trees. They are native to Mexico, Central America, and northern South America. They are now well established in the tropics and subtropics in Southeast Asia, Hawaii, the Caribbean, Florida, and Africa. The most frequently encountered species of guava is the apple variety of guava.

Guavas are typical plants with hard, dark leaves. The leaves are arranged opposite on the stem and are elliptic to ovate, 5-15 cm long. The flowers are white with five petals and numerous stamens. The generation Accara and Feijoa were previously included in the genus psydium. They are most often used by the larvae of many lepidopteran insects as food plants. the bacteria Erwinia psidii causes rot diseases in Apple Guavas. The fruits are highly appreciated by humans, many mammals and birds. The animals help in the dispersal of guava seeds over long distances along with their droppings. In some tropical regions, including Hawaii, many varieties have become invasive species. Several species have also been added to the rare species category due to habitat destruction. One species, notably the Jamaican guava, has become completely extinct.

Guava wood is used to smoke meat in Hawaii. They are also used in barbecue contests in the United States. Cuba leaves are also used in roasts, providing a smoky flavor and aroma to the meat. They are cultivated in many tropical and subtropical countries for their edible and highly nutritious fruits. Several species are grown solely for commercial purposes. Apple Guava is commercially available as a very popular variety throughout the world. Mature trees of most species can tolerate temperatures as low as 5°C, but young plants cannot survive. They are also grown as ornamental plants in temperate regions. The guava fruit is between 4 and 12 cm long or round, depending on the species. The outer skin is usually tough with a bitter or sweet taste. When unripe, the fruits are usually green, but turn yellow, maroon, or green when fully ripe. The fruits have a typical fragrance similar to that of lemon peel, but it is less strong. The pulp can be bittersweet and white or pink.

In Hawaii the fruit is eaten with soy sauce and vinegar. Sometimes a pinch of sugar and black pepper are also added along with soy sauce and vinegar to enhance the taste. In India and Pakistan, the fruit is often eaten raw or together with salt or pepper. The fruit is often used to make fruit salads. In Asia, guava pieces are often dipped in plum powder before eating. As the fruit contains high levels of pectin, they are used in the preparation of sweets, preserves, jellies, preserves, jams. They are sometimes included in the superfruit category, as they are rich sources of dietary fiber, vitamins A and C, folic acid, and dietary minerals, potassium, copper, and manganese. They contain four times more vitamin C than is present in oranges. They contain both guavas which contain carotenoids and polyphenols. They are part of folk medicine since ancient times. The extracts obtained from Apple Guava are used against cancer, bacterial infections, inflammation and pain. The essential oils obtained from guava also have some anti-cancer properties. The leaves are used to cure diarrhoea. The bark is believed to possess antimicrobial and astringent properties.