Ok not to worry, in addition to what Emma mentioned deleting the "cache" folder - if that didnt work, as well delete the "localcache" folder too ---- this happens when cache's get corrupted, and deleting them and refreshing the browser will re-create the two folders as well solving the issue.
additionally, Moodle runs based on its configuration file (config.php)
so whatever address you give into config files, Moodle will only be able to open using that, so if you open your config.php file, you'll see something like
$CFG->wwwroot = 'localhost';mentioned there.
in order to open the moodle using anything other than localhost, you have to change that address, so typing in http://127.0.0.1 will open moodle without any issues. but be aware, you wont be able to open moodle afterwards by typing http://localhost / localhost etc
In similar way, if you want to access moodle on local network, you'll be assigning that config.php file with address like http://192.168.1.20 (assuming this is IP of computer hosting moodle). this way typing that address on any computer will open that site, but again remember, now both localhost and 127.0.0.1 wont work (even on the computer where moodle is hosted), even on that computer you'll be typing http://192.168.1.20 to access moodle.