From Apple:
Apple today introduced a new version of iMovie with features that make it easier than ever to create beautiful edited videos on iPhone and iPad.Storyboards helps aspiring content creators and moviemakers learn to edit and improve their video storytelling skills with pre-made templates for popular types of videos shared on social, with colleagues, or with classmates — videos like DIYs, cooking tutorials, product reviews, science experiments, and more. Storyboards makes it easy to get started with flexible shot lists and step-by-step guidance on which clips to capture for each video type.For those who want to create a video even faster, Magic Movie instantly creates a polished video from the clips and photos a user selects, automatically adding transitions, effects, and music to the edit. Both new features include a range of styles to help personalize the final look and feel of a video, including titles, filters, transitions, color palettes, and music, all designed to work together.
Here's the new iMovie in action on my iPhone 12 Pro Max:
When done, exporting to a video will render everything out at your chosen settings, or you can even save to a new iMovie project which can be edited in more detail in the traditional way.
Another really useful aid to home movie makers on their phones, from Apple. A someone who covers both Windows and Android smartphones, the perennial question 'what should I use to edit video?' is only really easy to answer if the answer can be 'Switch to a Mac or iPhone'!