Before you create a single piece of content, Drupal asks you a question that no other tool has ever bothered to ask you.
Not "what does it look like." Not "where does it go." Not "what color should the button be."
What kind of thing is this?
This is a more interesting question than it appears. Sit with it for a moment.
You have been consuming content your entire life — articles, event listings, staff profiles, product pages, announcements, recipes, job postings. You know what all of these things look like. You have strong opinions about which ones are well designed and which ones are not. But you have probably never asked yourself what the parts of each one are. What fields does a staff profile have that an event listing doesn't? What makes an article an article and not a basic page? What is the minimum set of information that makes a thing what it is?
This is what Drupal is asking you. And it is asking you before you type a single word of content, because the answer shapes everything that comes after.
Remember the spreadsheet. A node is a row. A content type is the sheet in the spreadsheet - any spreadsheet can have multiple sheets. You design the sheet in the spreadsheet, before anyone starts adding rows. Change the columns later and you have a problem. Get them right at the start and the whole system rewards you for it.
Gerald never designed his columns. Gerald had a name column, a phone column, an email column, and then a notes column where everything else went — shoe size, preferred style, wife's birthday, the fact that he once mentioned he might be interested in the new boot line when it came in. Gerald's notes column is a graveyard of unstructured data that will never be useful at Christmas.
Drupal will not let you be Gerald. It will not let you start adding rows until you have decided what the columns are. This feels bureaucratic. It is actually the kindest thing Drupal does for you.
Different things are different. This sounds obvious until you try to build a website and discover how many people treat it as optional.
An event is not an article. An article has a title, a body, an author, a publication date, and a category. An event has a title, a body, a start date, an end date, a location, a registration link, and possibly a maximum attendance. These are not the same thing. If you store your events in the same content type as your articles you will spend the rest of your life explaining to Drupal why this particular article starts at 7pm and requires a parking pass.
A staff profile is not a product. A recipe is not a job posting. A testimonial is not a news release. Each one has different fields, different relationships, different questions it needs to answer, and different ways it will need to be used. Content types keep them separate, clean, and useful.
Drupal lets you create as many content types as your site needs. There is no limit. This is a generous feature that has led more than one site builder to create seventeen content types in an afternoon, including three called some variation of "Basic Page," with no description on any of them, for reasons that made complete sense at the time and are now lost to history.
When you create a content type, Drupal gives you a description field. Use it. Write it as if you are leaving a note for yourself at 2am a year from now, when you are staring at a list of content types trying to remember what you were thinking. You were thinking something. Write it down.
The most important work you will do in Drupal happens before you open Drupal.
It happens at a whiteboard, or a notebook, or a coffee shop napkin. It happens when you sit down and ask: what are the things on this site? Not the pages — the things. The entities. The records. What are their parts? What questions will I need to ask of them six months from now?
This is content modeling. It sounds technical. It is actually just careful thinking about the shape of your information — the thing Gerald never did, the thing the nephew never asked Gerald to do, the thing that would have saved them both a great deal of trouble at Christmas.
Drupal will build whatever you design. It is very good at that. It cannot design it for you. That part is yours.