What does ^M character mean in Vim?

Unix uses 0xA for a newline character. Windows uses a combination of two characters: 0xD 0xA. 0xD is the carriage return character.

^M

happens
to be the way vim displays 0xD.

You can remove all the

^M

characters
by entering the following:

:%s/^V^M//g

where

^V^M

means CTRL+V,CTRL+M and
is a way to entering characters

^M

into
vi. It will globally replace all occurrences of

^M

with
nothing.