What sort of specifications will the website developer need?
Until we have a way to do direct download from one human brain to the other, the process of describing what you want your website to look and function like is going to be a manual one.
But don't worry. There are millions of web sites out there and every one started with an idea that the site owner transmitted to the people who developed the site.

Here's how to do that...
You aren't going to be able to describe what you want to someone else if you can't describe it to yourself first. Get over this hurdle by simply writing out a paragraph or two that answers these questions:
- What is the purpose of my web site?
- Who is my target audience?
- What will I provide them that they can't get somewhere else or, if they can get it somewhere else - how will I do it better?
Work on that until you can have a one minute conversation with a friend or family member describing your new web site and they can walk away understanding exactly what it is that web site does.
Now you're ready to talk to your developer
In addition to the answers to the three questions you've already posed to yourself, your developer will want to know at least the answers to these Top 10 questions.
Depending upon the purpose, size and scope of your web site, there may be more questions that will need to be answered before the project can continue.
- Your development budget
- Your timeline
- Your branding preferences (logo, colors, graphics)
- Your menu structure (Home, About Us, FAQ...)
- The approximate number of pages you anticipate having on your site
- Whether or not you want a Content Management System
- E-commerce requirements (shopping cart, payment processor, etc.)
- Other features such as a newsletter, blog, contact form, etc.
- Links to competitors' sites.
- Search terms/keywords that are important to your site
While these are all one-line questions, you won't be providing one-line answers in most cases. Some of the questions may lead to further discussions which may, in turn, lead to further questions.
Why bother with all these questions?
Simple. It's easier and less expensive to make corrections to a web site design and infrastructure when you're still in the talking stage than it is to make those changes once development work has commenced.
Plus...
How can you expect to get what you want if you do know how to ask?