How system restoration works?

in my computer i installed a software about web protection. the password is hacked by my collegue from my email and forwade the recovery password link to her mail. after that i try to uninstall the software so i am not able to do so. after all i delete the all files from the "program file" folder in "c drive" by using command "shift+delet" but now my broser does not be able to open any site. after tha i restore the system to previous date. But after "system restoration" the full software is on its place and working.