Questions about the Psalms

I personally am very confused by the Psalms.  I do not really understand how to read them, or how to interpret it.  It's difficult because I have a hard time identifying the speaker of each song, and I also am unfamiliar with the historical context.  This might sound stupid, and perhaps ignorant, but who wrote all the stories in the Psalms?  How did these stories earn such an authoritative role in the world of religion? These are stories that make up the basis of Christianity.  I just find it interesting how quick people are to believe these stories, and view them as a type of spiritual guidance.  Especially when there are so many interpretations of each Psalm.  

I think it is very interesting that there are so many different interpretations of the Psalms.  I think it says a lot about religion.  When I was growing up, I used to believe that religious views were set in stone.  Raised Jewish, I used to believe that during, what is now called Passover, Moses parted the Red Sea.  I searched online for other stories of Passover and I, unfortunately, couldn't find any.  However, it is interesting because the story of Passover, or Pesach (as it is called in the Torah), probably comes from interpretation as well.

This might sound ignorant of me, but this is not my intention.  I am not a "religious" person, per say, however I would really like to understand what drives people to follow a certain religious belief.  I feel that when faced with multiple translations of the Psalms, I'd question the legitimacy of what I'm being taught.  However, what the knowledge of the Psalms having multiple interpretations has taught me is that religion is all subjective.  Each religious view is carried out based on each individuals personal interpretation.  I, now, feel that religion offers a set of guidelines for us to follow.  How we carry out these guidelines however is entirely subjective.  This is very different from my previous idea of religion, where I believed different religious offered single-minded approaches as to how one should live life.  I see now that this is not the case.