In Hinduism cast system can be observed , which is well known as Varna Bevastha (Cast System) in Sanskrit. In ancient time, such a system was created for suitability of society and to help each other. Varna Bevastha is nothing but the allocation of some dedicated work to a selected group of people as per their expertise. Basically 4 varna mean communities are seen. Those are Brahmin, Kshatriya, Shudra and Vaisya. All four varnas are most important parts of society like the four pillar of any house. Responsibility of Society cant be put on a single community (Varna) people. As we to build house on a single pillar. Among these four varnas Brahimins are most respectful varna (Community) than all other varna or community. One question will be raised in mind that "what is the meaning of Brahmin". Brahmin is sanskrit word which mean the person who follow Brahma (Soul). Another way this varna people are called Brahmin due to Lord Brahma who has created this whole universe. It is consider that the Brahmins are born from the head of lord Brahma. In society, Brahmins were most respectful because of there knowledge. They were teachers in society, they were advising peoples about everything like what is good and what bad.
The second highest varna (Cast) is kshatriya. It is like Kshatra (Region) and triya (Protector), Kshatriya means the cast who protects there mother land from external enemies. Kshatriya are warrior and they practice the techniques to fight with opponents. Kshatriya protect other varna people. Mostly Kshatriya were king. It is considered that Kshatriya are born from the Chest of Lord Brahma. It was called as second pillar of ancient Arya society. They were allowed to perform cruel activities like hunting.
The third varna is Vaisya, these peoples were less educated and for their living hood. They were doing farming, rearing animals and doing business. Vaisya mean the peoples who perform low quality works. They also were working as servant for king and rich peoples. Vaisya means who sold their service for money. Another meaning of Vaisya is whose grade is low and having uncontrolled desires. This varna is considered that born from the thigh part of Lord Brahma. It can be called as third pillar of ancient Hindu society.
The fourth varna is shudra, and it is last varna and fourth pillar of ancient Hindu society. Shudra or Kshudra means small whose living standards are very poor and not accepted in the society. Such kind of peoples are called Shudra. Whose mentallity and living standard quality is small or lower than the social standard. Shudra varna peoples are uneducated, speak bad language and behave unlawful. They live life with meat, alcohol and sex as they desire. They didn't have control on their desires. They were not involve in spiritual activity. They were doing business of skin.
Varna arrangement were depending on the quality of people in society. It was not being transfered from father to son and from son to grand son. Suppose a person is brahmin having good knowledge about vedas, puranas, spiritual, Ayurveda, astrology and science. The son of that person having the quality of shudra and live life with alcohol and meat can't be said as brahmin. Similarly a person is shudra and his son has good practice over the vedas, shastra, upanishads and vyakaran. Then his son is deserve to be called as brahmin.
In Hindu puranas, there are many examples, where peoples have changed their Varnas. Like Brahmrishi Vishwamitra, before becoming a Brahmrishi, Vishwamitra was a King means Kshatriya. After gaining knowledge, he became Brahmin and depicted as Brahmrishi. Another example is found in Ramayan, in which Maharishi Valmiki was also an shudra, whose work was to do stealing and dacoiting. After getting knowledge by hard penance, he became Rishi Valmiki and composed Ramayana. In olden days Casteism doesn't passes from generation to generation for a family. But it was the division according to thier quality of work and professionalism. We should understand that as a doctor cann't work in place of a engineer and an engineer can't work in place of advocate and an advocate cann't work in place of Barbara. As in modern days, we have divided the professionalism as per thier achieve knowledge. Similarly, these four Varnas were divided as per their achieve knowledge and behaviour. As it is not necessary that the son of a doctor should accept the profession of doctor and he might become a engineer. Similarly, in ancient time, it was not necessary that the son of Brahmin will be a brahmin. As time passes, Brahmin father transfer his knowledge to his son and a Kshatriya transfer his knowledge to his son. This process was continue further and it become limited to particular family and relative. In later stage, it was misunderstood. Thank you