"Pages" that display other websites.

Page of posts example based on Twenty Eleven

Missed this bit:

I was under the impression that when I type a new Post and assign categories to it, it appears on my Main Page by Default and a copy is redisplayed on your “Page of Posts” page.

That assumes that you don’t alter the standard query/Loop in the theme’s index.php template file. However, using query_posts() again, you can exclude specific categories (for example) or opt to display just posts from one category.

I’ve used this along with “page of posts” to create separate listings for posts based on any number of criteria. For example, the main posts page might just display posts in the News category. another page might display posts from the Main Courses category. A third might display featured posts (posts that have a specific custom field assigned to them) from all categories except News, etc etc.

Once you get into custom queries, the possibilities are (almost) endless. Have a look at https://codex.www.ads-software.com/Function_Reference/WP_Query for all of the possible parameters that you can also use with query_posts().

Ah, back to the hand-recoding of WP.

As I noted, I was hoping for a simpler solution (and one that I might not have to redo after every update.)

There might be some plugins that can help you to achieve the same end but, in my experience, they can fail if the author doesn’t update them regularly to keep up with core updates. I’ve ended up sorting out quite a few sites recently because of these kinds of issues. But if you do want to try the plugin route, something like https://www.ads-software.com/extend/plugins/query-wrangler/ might help.

one that I might not have to redo after every update

Not sure why you’d need to re-do any custom queries. Once they are in place, they can normally be left alone to work quite happily. The only proviso here would be if you are customising the current default theme – which would be a big no-no. In fact, with any downloaded theme, I’d suggest using a child theme as a way of keeping your customisations safe whilst still allowing you to update the parent theme without any worries.

If I modify any WP PHP file by hand, if that file is altered in the next update, I would have to edit the page all over again.

“Child Themes” sound interesting, but once again, sounds like far more work than I’m prepared to do at this time (I’m considering a Theme overhaul in January and might tackle comprehensive Theme modifications/additions at that time.

I’ll look into “Query Wrangler”. Hopefully, the kind of functionality I’m looking for will be built into WP 4.0.

If I modify any WP PHP file by hand, if that file is altered in the next update, I would have to edit the page all over again.

A core WordPress update will not touch your theme files. The only way they can be changed is if you update/over-write the theme.

How do you call “pageofposts.php” without altering core files?

The entire code is within a custom page template file in your theme. drop the code at https://pastebin.com/ueb3pDqd into a new template file in a simple child them of Twenty Eleven and apply it to a static Page.

You can download a pre-made Twenty Eleven child theme from here if you need it.