In plain English
A database is basically a filing cabinet the website reads and writes to on its own. Bookings go in, orders go in, customer details go in. It's laid out like a spreadsheet: rows and columns. One row per booking, columns for the details, name, date, party size. The back-end reads it, writes to it, updates it. You never have to open it up and type anything yourself, the code just gets on with it.
A worked example
The café's bookings table has one row per booking, with columns for name, date, time, party size, phone number. Someone books through the website, the back-end quietly adds a new row. As the café owner, you'd see this in a dashboard that genuinely looks like a spreadsheet, you can scroll through it, click into a booking, add a note if you fancy. There'd probably be a menu table too, dish names, prices, descriptions, anything that changes often enough to need updating without touching the code.
Getting set up
Static sites need none of this. When you do need a database, Supabase is the common pick for small sites, and it's free to start. Sign up with GitHub or an email address, spin up a project, and there's your table editor, looking exactly like a spreadsheet. Build tables right there, no code required for the basics.
The usual mix-up
People mix up the database with storage. A database holds small, structured facts, rows and columns. Storage's job is big files, images, PDFs, that sort of thing. Different tools, different jobs.