Who is River Song

In the season 4 in episodes Silence in the Library and Forest of the Dead there was woman that show up name River Song said she the wife if the Doctor and know his rely name to. In season 5 in episodes The Time of Angels and Flesh and Stone and River Song show up them to and have a journal about her and the doctor. And in the episode same one told the Doctor that River Song killer a great man that save the world. When hard that I know how he was take about she killer the Doctor same time in the future when he had a new face. One more think and the doctor know how she rely is but I hope he find out soon before done it in the time it happens.