What will restoring my Iphone 5 do to my phone if its done by itunes?

What will restoring my Iphone 5 do to my phone if its done by itunes?

Help me please! I connected my phone to Itunes for my update, and once it said that it was finish it said it was on recovery mode. And the only way for me to use itunes will be if i restore it through itunes. When i unplug my phone it has a picture with a circle with the Itunes logo, and the connection of the cord. I tried unplugging and my phone doesn't turn on the same screen keeps popping up with the logo. Will this affect anything on my phone? I need fast response.