Well that is because you merged upstream commits and there is one that modifies the same lines of code as you did, normally git says "merge conflict" and adds those arrows, like so:
````
<<<<<<<< HEAD
foo
========
bar
>>>>>>>> merged commit
````

Where `foo` is your own code and `bar` is the remote code. Then you have to merge manually ie. determine what should be kept from both sides.
After you are done you usually cleanup the arrows and equals signs then `git add` `git commit`.

You can find more info on that here: http://githowto.com/resolving_conflicts