Many were craving for a "Lost" series finale explanation after it aired.  While many questions were answered, others were unsolved; many people still don't quite understand the entire picture.  After six seasons of twists, delving deep into themes about human nature, the afterlife, and the paranormal, "Lost" fans are still unsure of the finished product. How did "Lost" end?

The Man In Black Versus Jacob.  One of the more ambiguous parts of the "Lost" series finale was the end of the conflict between Jacob and the Man in Black.  After we discover that the smoke monster was the result of Jacob throwing his brother, the Man in Black, into the heart of the island, we can see why Jacob was so paranoid about making sure he never escaped.  The Man in Black (MIB) represents the evil side of humanity, and if MIB was to escape, he would cause irreparable damage to the entire world.  Although Jacob dies, he manages to pass on guardianship of the Island to Jack, who uses his gifts to ensure that MIB cannot escape.  When Jack discovers that MIB's immortality is due to the keystone that sits at the heart of the island, he allows Desmond to unplug it so that he can kill MIB, but sacrificing his immortality in the process.  

What Is the Island?  Though many theories exist as to what exactly the Island is, "Lost" viewers can assume two things.  One, the Island itself is a living entity; it attracts people to it through supernatural phenomena.  While the source of this phenomena seems to be due to abnormal pockets of electromagnetic radiation,  it produces incredible affects on those that live on it, including the remission of Rose's terminal cancer, John Locke's ability to walk, and Desmond's ability to sense the future.  Viewers can also assume that the Island acts as a container to house the evil of humanity, which is manifested as the smoke monster and his other form, MIB.  When Desmond unplugs the cork at the heart of the Island, it begins to sink, confirming the theory that it somehow prevented evil from escaping the Island.  Fortunately, Jack was able to utilize that small window to kill the MIB before he could escape.   

Desmond's Role.  Though it's no secret Desmond can predict the future, the real reason he is special is because he has the ability to absorb unhealthily large amounts of electromagnetic radiation, allowing him to unplug the cork at the heart of the Island without dying and letting him propel into the alternate reality.  When Desmond is thrown into the alternate world, he becomes aware of what happened in the other reality, and begins the task of uniting the other survivors so that they too can connect with each other and their memories on the Island; this appears to be the true task that Desmond was selected for.  

What Is The Flash Sideways Reality?  The flash sideways world is a reality that the "Lost" survivors created for themselves to help reconnect with each other.  In the real world, the time in every character's life when they made a difference or significant change for the better was when they were on the Island.  Throughout those days, several characters died, creating emotional rifts between the survivors, who had become extremely close with those they once considered strangers.  But when anyone died, they wound up in the flash sideways reality, which acted as a sort of limbo until they all reconnected.  Through Desmond's efforts, the major characters found each other, and were finally able to move onto the afterlife.  In the flash sideways world, time did not follow a linear path: every character died at a different time, but they wound up in that reality where time was not defined.  This is seen by Hurley thanking Ben for being a "great number two," because he worked with him on the Island for a much longer time.