The language of Angels: Enochian

          Enochian symbols, sigils, and speaking is used many times when the angels become a big part of the brothers fate. The language is used by the angels up in heaven and they are the only ones who can really understand it unless they are prophets of the lord like chuck Shurley.
          The symbolic language can also be used against the angels at times too. If an angel wants to keep something hidden from all angels it puts sigils on it which "hides it from angel radar".
                     

            When the angels were after Sam and Dean to try and force them to say yes to Michael and Lucifer, Castiel carved the Enochian sigil onto their ribs so that no angel, not even him, could detect them down on earth. Around this time, Castiel had to get a cell phone to stay in touch with the brothers. After a while, the angels caught onto this and made fun of him.
               
Castiel also showed Same and Dean the Enochian Sigil of Protection. This sigil is used in times of quick thinking, so if the brothers are swarmed with angels all surrounding them, if they have this sigil drawn in blood laying around they can send all the angels in the area all jumbled up somewhere else around the world. It gives them enough time to either get out of where they are, or get prepared for a fight.

          The brothers use more sigils when Balthazar comes and tries to help the brother's get away from Raphael. He wanted to kill them, not hand them over to Michael and Lucifer. So Balthazar uses a sigil to jump the brothers to a different reality where they were no longer hunters. So instead they were actors on a television series called supernatural. It confused the brothers to the point that they didn't know what was going on anymore, until Raphael came trying to kill them, making everything more realistic for them again.