Files with local modifications

After upgrading, it gave me a long list of files which it said had local modifications.



What does that mean and what should I do about them.



The files are prepare.php, controllers/customer/checkout.php, controllers/admin/categories.php, and a bunch of var/skins_repository and skins files.



When I view the files, it has areas hi-lited in pink and green, but not sure what that means or what I should do.



I don’t recall making changes to any files, except one file, can’t remember which, that caused cs-cart to go directly to checkout after a customer clicked the add to cart button.



Any one able to explain this to me?



Help will be appreciated.



Lewis

2.0.7, but going back to 2.0.6 until bugs in 2.0.7 resolved.