That symbol is simply showing where you have placed the carriage returns.... (which you press to force your text onto a new line)... You have managed to turn on the *show carriage return* by accidentally clicking on it (it's on the "Standard" toolbar, over on the right hand side at the top of your monitor). It will also display spaces and tabs. I actually prefer to have it switched on (it's just a toggle) so that I can see where my tabs and spaces are.
It's all derived from them thar olden days when typists used manual typewriters and at the end of typing a line of text on a piece of paper, they would have to manually return the carriage which held the piece of paper - the keys stayed in the same place, it was the platen carriage assembly that moved .... Similarly, tabs were preset amounts that the platen jumped (a definite number of spaces each time) so that type could be lined up row by row.
See what useless information some of us have in our brains :)