Source of food
There are two main sources of food in the world for all human beings – namely plants and animals.
*    Plants as Source of Food : Foods obtained from plants are of different types — cereals, pulses, vegetables, fruits, oils, sugar, tea, coffee and spices. 
(i)  Cereals are the most important sources of food for man and animals. They are rich sources of carbohydrates. Three most important cereals are wheat, rice and maize. These cereals are obtained from grains (biologically, grains are fruits of a plant).
(ii)   Pulses or Legumes (commonly called 'dals') are rich in proteins and are obtained from plants.
(iii)  Vegetables are rich sources of vitamins, minerals and roughage.Water content in vegetables is high (70 to 90 per cent) and their food value is low. 
(iv)  Fruits have high water content, low food value, but are rich in minerals and vitamins. In common usage, the term 'fruit' is used for those which are usually eaten without cooking. 
Common fruits are banana, mango apple, grapes, pineapple, guava, orange, litchi, and so on. 

(v) Sugars are produced by the green plants through photosynthesis. Chief sugar producing plants are sugarcane and sugarbeet. 
In case of sugarcane, the plant part used is the stem, while in sugarbeet, it is the root. 
(vi) Tea and coffee are common beverages, Tea is obtained from leaves, while coffee is obtained from seeds.
(vii)   Spices have no food value and are used for adding flavour to food. Before the advent of refrigeration, spices were also used for preserving foods.
The important spices are pepper (kali mirch), cardamon (ilaichi), ginger (adrak), turmeric (haldi) and chillies (mirch), cloves (loung), saffron (kesar), fennel (saunf), cumin (jeera), coriander (dhania), asafoetida (heeng), fenugreek (methi), nutmeg (jaiphal) and thyme (ajwain). 
(viii)    Oils : Oils are rich in fat and provide energy. Cotton, groundnut, mustard, coconut, soyabean and sunflower seeds give us oil.
(ix)    Medicines : Some plants have medicinal value and are used for curing certain diseases especially in Ayurveda. Mint, Basil (tulsi), ginger, fenugreek (methi), etc. are used in medicines.