Your problem is rather simple. Looks like you are using XAMPP.
it is likely that either your firewall (anti-virus software, internet security, endpoint... are some of the names taken by these software) or you have some other software that is blocking port 80.
Please try to stop those software and you should be good to go.
If you probably give the OS, the webserver used it will be a little easy to help you better.
This issue may be because another application/service acquired port 80.
Please check your XAMPP control panel for the services that are currently running.