What It Is
A child theme is a small add-on theme that sits on top of a main theme, called the parent. It borrows all of the parent’s design and features, and holds only your changes, such as custom styles or edited template files. Think of it like a clear overlay on a printed map. You draw your notes on the overlay, and if the map is replaced with a newer edition, your notes are still there.
Why It Matters for Your Business
This matters because themes get updated for security fixes and new features. If a developer edits the parent theme’s files directly, the next update can silently wipe those edits, and suddenly a salon’s custom booking section or brand colors are gone. With a child theme, the parent can update safely while your customizations stay in place.
Good to Know
You only need a child theme if someone is editing theme code or files. Changes made through the WordPress Customizer, the Site Editor or the "Additional CSS" box are stored in the database and usually survive updates. If you hire a developer for custom theme work, ask directly whether they are using a child theme, and make sure you have a backup before any theme update.