The U

How y'all doing, i'm completely new to this forum and to android (1 week). i have a question and i hope im in the right place. i bought a transformer prime infinity and while i have got to grips with most of it a few things i not sure about. when i type an email every now and then a blue thick arrow/curer appears under what im typing. why does this appear?? and what is it for?? how do i make it go away?? this also stops me from using my spell check when i have a red line under my word. this is why i need to know how to make it go away. this is a very basic 101 question but i just cant figure it out. thanks for any help you can give me.