Question about PSD / WP

Essentially, you've got the right idea. WordPress themes are composed of a set of specific files that the WordPress core looks for when it goes to render a page. The basic one is index.php. You can break index.php up a little bit into header.php, index.php, and footer.php (because the header and footer are going to stay constant no matter what page we're on). Let's also add something for looking at single posts (single.php) and something for looking at pages (page.php)

So now we have 5 files that define our basic template. We can now do a little PHP coding in each one to tell it what we want to render:

header.php: Will render the html headers, include stuff from the wp core, and set up the header of the page.

footer.php: Will render the footer, close out the main html tags, and add javascripts/analytics/etc. that wp core wants to include in the bottom of the page.

index.php/single.php/page.php will all display the content of our blog in the way that we see fit. They will start by including the header, add whatever code we want to display things on that type of page, and then include the footer.

Put them all together and include a basic CSS file (called style.css) and a screen shot (screenshot.png) and you have a basic WP theme.

WordPress is hugely extendable though. You can further break-up templates and have different sidebars or modules that you include in a similar fashion to the header and footer. You can add different php files to deal with Archives, Search Results, 404 errors, Custom page types, Custom Taxonomies, Categories and Tags, Author information, and you can even create your own special functions in a file called functions.php.

So, the goal as a theme developer, then, is to take a design (PSD, JPG, Sketch on the back of a napkin, whatever) and translate that into a comprehensive theme file.

Lots of people create child themes and skin template frameworks like Thesis or Genesis or Thematic. Most of the coding work, and a substantial amount of the more difficult styling and layout is already done, and it's just a matter of adding the relevant CSS/Images to make it look exactly the way you want it.

I often use a theme called Starkers from Elliot Jay Stocks (I can't add a link, but you can google it) which is stripped down to barest essentials, and then I build off of that. It has the basic components in place, and there's no need to re-invent the wheel. I can add on custom page styles, and new modules that I write, and I have full control over the style of the whole thing.

So, basically, that handful of files grows into a collection of anywhere from 15 to 50 (excluding image files), depending on the modularity and functionality that is included in the theme. You can do a significant amount of stuff with WP themes. That's why I am particularly fond of it as a designer/developer.

If you're curious about how to become a theme developer, drop me a PM, and I'll point you in the direction of some good resources for learning that very process. It takes some time, and some effort. You have to get comfortable with the idea of writing code, and so forth. And if you just want to get a new theme, it's probably better just to hire somebody professional to build you one the way you want it. But if you're interested in learning how to do it, it can be a fun challenge.

A PSD file just provides a conceptual guideline to work from as you go about building a site. Typical workflow is that the designer puts together a conceptual PSD, and passes that off to the developer, who chops it up into whatever images they need to grab, and uses it as a guideline for building out a theme-be it from scratch, or by fiddling around with another template.

You're not the only one who's had troubles with designers. That's why, when you're involved in a project that has hired a designer, you need to be higher on the pecking order, preferably even having input when the brief for the designer is created. Most designers know and are used to working within limitations and according to guidelines - they just don't like having those handed to them at the last minute or after they've completed part of their work. No one likes doing things twice.