help mod rewrite

[stratosphere]

can anyone please explain to me how modrewrite this in .htaccess
example:
mysite.me/index.php?do=viewuser&who=1
modrewrite to
mysite.me/who=1

[BDplanet]

u can re-write it

http://mysite.me/index.php?do=viewuser&who=1
to
http://mysite.me/viewuser/1.html

by using dat .htaccess

RewriteEngine On
RewriteRule ^([^/]*)/([^/]*)\.html$ /index.php?do=$1&who=$2 [L]