When you see http://localhost/, or https://127.0.0.1/, it refers to network address of the computer you’re currently working on.

Localhost is a loopback address, associated with your computer’s local IP which defaults to 127.0.0.1 for IPv4, or ::1 for IPv6

If you have a configured webserver running on your computer, you may see a webpage when you open https://localhost/ or http://localhost/ in the browser.

You might also ping localhost, here hos it looks in my case:

ping localhost
Pinging DESKTOP-HCJ9KLE [::1] with 32 bytes of data:
Reply from ::1: time<1ms
Reply from ::1: time<1ms
Reply from ::1: time<1ms
Reply from ::1: time<1ms

Ping statistics for ::1:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 0ms, Maximum = 0ms, Average = 0ms

Please take note – my local IP is displayed as ::1, as my computer is connected to the network that has IPv6 addresses