Bhagavad Gita Verse 44, Chapter 18

krishigaurakshyavaanijyam vaishyakarma svabhaavajam |
paricharyaatmakam karma shoodrasyaapi svabhaavajam || 44 ||
 
Agriculture, cattle rearing and trade are natural duties of the vaishya. Service oriented actions are the natural duties of the shoodra.
 
krishigaurakshyavaanijyam : agriculture, cattle rearing and trade
vaishyakarma : duties of the vaishya
svabhaavajam : natural
paricharyaatmakam : service oriented actions
karma : duties
shoodrasya : of the shoodra
api : also
svabhaavajam : natural
 
Shri Krishna now describes the duties of the vaishya and shoodra varnas. The mental makeup of vaishyas prods them to raise, invest and trade in capital, goods and services. Although the shloka mentions agriculture, cattle rearing and trade, the broader concern of vaishyas is money. They are guided by the economic motive behind all their actions. Vaishyas play a critical role in any society by starting and maintaining the engine of the economy. They ensure that the needs of society are met by providing what it needs at the right place, time and for the right price.
 
Shoodras comprise the service sector. They pursue occupations where they can serve society in an individual capacity. They have a lower tolerance for risk as compared to kshatriyas and vaishyas, since the proportion of rajas is lower. Therefore, they prefer to work in occupations where they render their services to society and in return, are compensated for their services appropriately. Like any other varna, their natural inclination to do a certain type of work is enhanced by gaining the right skills and training needed to perform their tasks well.
 
We should refrain from harbouring any notion that one varna is better than the other. The human body itself is said to be made up of four varnas. The mind is a braahmana, the hands are kshatriyas, the thighs are vaishyas and the legs are shoodras. The body cannot function properly if any component is malfunctioning. Similarly, society cannot function when one varna does not perform its natural duties. Societies that encourage each individual to realize their full potential tend to flourish. With this shloka, Shri Krishna concludes the description of the four varnas.