Login for access to certain pages or parts?

Could someone kindly recommend either a simple tute on the
subject or else a simple guide of the steps to be taken to make a
login page for a website so that a few password issued people can
view a particular set of pages or section of a website. It is not
needed to be like Fort Knox, just a simple thing like say a
commercial site where only wholesale customers are allowed into
some set of pages giving special information for their eyes only.

I suppose it depends on the type of server as to what is best,
but assume a Unix with PHP enabled. I have got to the stage of
being able to use php includes both for Unix commercial servers
and my own on my Mac (in no small measure due to guidance on this
ng a while back).

I am easily blinded by science! I know roughly what an .htaccess
file is and I have access to more than this on my own server, but
not more on commercial servers that host various sites I have
made or maintain.

--
dorayme
.