This thread is closed.
This thread, your question, is far too broad, and is addressed by multiple chapters of grammar books.
Our rules require specific examples.
I suggest you use the Search Engine or WR Dictionary to review the many prior threads on the use of "se".
For a start, see the threads list here:
http://www.wordreference.com/es/translation.asp?tranword=impersonal
If you have a specific example that is troubling you, please feel free to ask about that specific case.
Also, before opening a new thread, please review our titling instructions and context explanations.
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