How g makes loop in Vim ex command script

Question

Consider the following Vim ex command,

:let i=1 | \'<,\'>g/^/ s/^\\ *-/\\=i/ | let i+=1

It replaces the heading dash with ordered number

Answer 1

This is the general pattern of a :global command:

:g/foo/command

Because everything after the second separator is considered as one command, the counter is incremented each time the command is executed: one time for each matching line.