What is the purpose of source?

The purpose of a source depends heavily on the context. To help me give you a more specific answer, could you please clarify what kind of source you're referring to?

For example, are you asking about:

* Sources of information: like books, articles, websites, or people?

* Sources of energy: like coal, oil, or solar power?

* Sources of code: like libraries or frameworks in programming?

* Sources of water: like rivers, lakes, or aquifers?

Once you tell me what kind of source you mean, I can explain its purpose in more detail.