Varna in sanskrit means class, type or color.
It is known in the western world as the caste system, but hardly anyone understands what it is really about or how it works or is supposed to work, since today the system got perverted a lot.
In the vedics it is called "varnasrama dharma" which means carna=class asrama=system and dharma= right action, so it is the classsystem of right action.
The original caste system is not something that has been invented by man and it is not part of some religion or religious practice.
The caste system is a universal principle created by god and it transcends all human societies and religions.
In any human society you have the caste system, if recognized or not, since the caste system is the natural god given foundation of human society.
1. Brahmana - The brahmana class is the highest class, it is the class of those people who are the most intelligent and mainly take part in intelectual work, it is usually referred as the priest class, as most times those peoples job in society is that of a priest or priest like job. In modern times we refer to those people as scientiests for example. Basically any activity that requires the highest intelligence in the society is done by the brahmana class. Those tasks are often done by non qualified people, especially in our "modern" times, but this just leads to chaos and misery, as unqualified people cannot do the tasks properly and the result is of no benefit for society.
2. Kshatriya - The kshatriya class is the second highest class, it is the warrior class. People in the warrior class are often, of course warriors, but also kings and goverments are kshatriya class, or should be. The main attribute of a kshatriya is strengths and bravery. Kshatriyas offer protection for the society and rule the society, a king for example is a kshatriya. The ruling class receives the highest benefits in society, they are the richest and most powerful, but they also have to pay the highest price, since they have to fight and die in a case of war, where protection is needed.
3. Vaishya - The vaishya class is the class that feeds the society, like farmers and traders. In modern times it would be the businessman. So everyone who has a business and produces and or distributes goods is a vaishya. The vaishya is more an organizer who has a business and manages the workers and the production of goods.
4. Shudra - The shudra class is the lowest class and those people are simple workers. Every person who has a simple job and works for a salary is a sudra. In modern times almost everyone is a sudra, since almost everyone now is a simple worker for someone and receives a salary. These are the signs of a sudra.
5. Pariahs - The pariahs are not officiall a caste. Pariahs are all those people who do not qualify for any of the casts and are therefore considered without a caste. Those people usually live like animals and are treated as such by the rest of the society. They are also labelled "untouchables" since they are considered so dirty, that you should not associate with them. In modern times those people would be those that we call "antisocial" people, who are usually unemployed and/or addicted to drugs.
The caste system is not cruel or unfair, it is a system that allows everyone to live according to his nature. The system exists anyway, since it is given by god or nature, it always existed and will always exist.
So if people live according to this system it will benefit the whole society, as everyone is treated as he deserves.
And please don't mistake this for the caste system that exists in our time in india that has been perverted. The original caste system goes by qualification, so whatever qualification you have, you can do those acitivities and be in that caste. But now they perverted it, so you can only be in the caste you are born in or only do the job your family is doing. In a perfect society this will automatically be the case in all or most of the cases, but the main qualification is always what abilities you have, it does not matter in what family you are born, if you are intelligent enough you can be a brahmana or any other caste.