[Tugindia] use of % symbol at end of lines

[Sreejith Pulloor]

Dear All,

I would like to know whats the use of % symbol at the end of a line

for example (from mathmode.pdf by Herber Vo\ss) page 15  section 3.2.1

1 \ makeatletter 2
\ newcommand {\ be }{%   ---------> whts the use of this %
3 \ begingroup
4 % \ setlength {\ arraycolsep }{2 pt}
5 \ eqnarray % ---------> whts the use of this %
6 \ @ifstar {\ nonumber }{}%  ----------> here also  whts the use of this %
7 }
8 \ newcommand {\ ee }{\ endeqnarray \ endgroup }
9 \ makeatother


i really dont know why we need to put % mark sometimes on the end of 
certain lines
could some one please explain
thanks
sreejith