If you see a website offering an iMovie 10.2.5 DMG download, it is either:

If you are running an older Mac that cannot update to macOS Catalina or later, for you.

It’s a solid, user‑friendly video editor for beginners—great for quick trailers, basic cuts, and 4K editing. However, professionals may find it limiting compared to Final Cut Pro or DaVinci Resolve.

Double-click the .dmg file to open it. A new window will appear showing the iMovie icon or a .pkg installer.