iMovie is Apple's flagship program to create and edit movies on your Mac. User friendly, iMovie makes it easy to turn your home videos into polished films.
Incredibly easy to use
iMovie works by importing your movie and then allowing you to cut and paste bits of it together, much as you would with a word processing application. Adding soundtracks is a breeze thanks to integration with iTunes, while images can be just as easily imported from iPhoto and the Photos app (it is even possible to apply an automatic Ken Burns effect to panoramic shots). There is also a Voiceover button below the viewer to allow you to easily add narration.
If you just want to cut something for YouTube, an integrated uploader makes sure your creations go online instantly, although I sometimes find this fails to upload properly or doesn't tag the video correctly. You can also email your creations, or share via. Youku and Tudou, in app.
Easy to add a touch of class
There are tons of trailers and templates for you to choose from that make your movie look far more polished than would ordinarily be possible. By the time you've finished, your raw film should look amazing. There is even green screen and blue screen support if you want to start playing with special effects.
iMovie can be fussy with formats - it works best with DV format films and trying to import other formats may not work (though Sony's XAVC-S and AVCHD are explicitly supported).
Not for Pros but great for the home user
Advanced video editors will find that iMovie lacks specialist editing functions but for most people, iMovie turns you into a pro with minimum effort.