Do you know why localhost = 127.0.0.1

Today I see a blog and get the answer as below:

Open 'C: \ windows \ system32 \ drivers \ etc 'Open the 'hosts', the contents as below

# Copyright (c) 1993-2009 Microsoft Corp.
#
# This is a sample hosts file used by Microsoft TCP/IP for Windows.
#
# This file contains the Mappings of IP addresses to host names. Each
# Entry shoshould be kept on an individual line. The IP address shold
# Be placed in the first column followed by the corresponding host name.
# The IP address and the host name shocould be separated by at least one
# Space.
#
# Additionally, comments (such as these) may be inserted on individual
# Lines or following the machine name denoted by a' # 'symbol.
#
# For example:
#
#102.54.94.97 rhino.acme.com # source server
#38.25.63.10 x.acme.com # X client host


# Localhost name resolution is handled within DNS itself.
#127.0.0.1 localhost
#: 1 localhost

Do you know why localhost = 127.0.0.1