1. He has finally paid his debt to society.

(What does 'society' mean here? Did he pay the debt to a bank or just the society he lives in?)

Society means the society in which he lives -- his country, village, family, and so on.

This phrasing -- "his debt to society" -- usually means he has served time in jail or prison after being convicted of something that harmed his society. That's why it's considered a debt to society and not to any one person. It's not usually money, unless he has to pay a fine.

In the given statement, "society" refers to the larger community or the society in which the person lives. It doesn't specifically mean paying a debt to a bank or any financial institution.

To understand the meaning of a word or phrase in a specific context, you can consider the following steps:
1. Read and analyze the sentence: Pay attention to the words surrounding the word or phrase you want to understand. In this case, "debt to society" indicates a broader obligation or responsibility.
2. Consider the broader context: Look at the context of the sentence or paragraph. In this case, it is implied that the person had a debt or wrongdoing toward society as a whole.
3. Define the word or phrase: Consult a reliable source such as a dictionary or online resource to find the meaning of the word or phrase you're trying to understand. In this case, "society" refers to the community or the larger social group.
4. Connect the dots: Combine your understanding of the definition with the context of the sentence to grasp the intended meaning.

By going through these steps, you can develop a deeper understanding of the meaning of words or phrases in different contexts.