What is the use of the "s" parameter of google map? -

i've noticed there sub strings of "galileo" in urls of google map tiles, http://khm2.google.com/kh/v=84&x=11&y=8&z=4&s=g or mt3.google.com/vt/lyrs=m@152&hl=zh-cn&x=1&y=7&z=4&s=ga.

and parameter calculated codes below:

string secword = "galileo"; int seclen = ( 3 * x + y ) % 8; string sec = secword.substring( 0, seclen ); 

but use of parameter, since seems can correct map tiles if remove or change randomly?

here 1 mention:

output=embed outputs html suitable embedding in third party sites, works presence of encrypted s= param, presumably stop arbitrary content being included.

http://picchiri.wordpress.com/2010/02/24/google-maps-parameter/