iMovie is a non-linear video editing program for Macintosh
iMovie was announced with the new Firewire iMac line, the iMac DV, at the October 1999 Macworld Expo. Apple iCEO Steve Jobs declared video editing "the next big thing" and wanted to put its power into the hands of the masses, at a $1299 starting price. Reviewers considered it a "Final Cut lite," and while it lacked many of the more powerful features of its $1000 software cousin, it was perfect for simple home movies. You simply plugged in a Firewire video camcorder and it copied the film to the hard drive, and you could then edit the film with transitions, special effects, transitions, titles, soundtracks, and credits, and place it back into the camcorder. Later updates allowed you to post an iMovie directly to your mac.com homepage, which at the time was free for all Mac users.
Originally it was bundled with the iMacs only, then Apple offered it for sale once it became obvious that various other users desired it (selling their copies on eBay, pirating it, etc.). They later bundled it with their Firewire iBooks, the "my retinas it burns" Lime Green iBook and the Graphite iBook SE, as well as their entire Macintosh line. Also, Microsoft tried to copy its success with "Windows Movie maker" which was panned by critics as being too complex compared to iMovie.
Apple later released iMovie 2, which updated many features that people requested, giving some more advanced features like clip splitting and different clip speed adjustment, (I think) as well as integration with Apple's iDVD. It acquired a "Brushed metal" interface like other apps such as Quicktime player. iMovie 2 was one of the first Apple apps ported over to Mac OS X at its launch, but didn't make it in time to be packaged on the install CD. Users who bought Mac OS X 10.0 on its launch date, March 24, 2001 (nearly a requirement for a Mac geek like me to know these dates), could download iMovie 2 for free off Apple's website. It later performed much better under the Mac OS X 10.1 release about 6 months later.
iMovie 3 was released as part of Apple's iLife suite, where it became much better integrated with iTunes, iDVD, and iPhoto. iMovie could easily interact with the other apps, getting a song from iTunes or a photo from iPhoto or exporting to iDVD with chapters. One of the hyped features was a new photo transition tool, known as the "Ken Burns effect," where you pan and zoom over a photo.
iMovie 4 was released with iLife '04, when Apple decided to release iLife updates annually. New features included allowing you to edit multiple clips and transitions at once, trim clips directly in the Timeline without losing your original footage, sync video and audio with alignment guides, use an iSight camera to import live video directly into iMovie, share movies using Bluetooth, and keep track of key frames in your Timeline with bookmarks.
As of now, Apple released iMovie HD as part of the iLife '05 pack, which allows you to edit your movies using the new widescreen HD camcorders that are just coming out now. It also includes a new feature called "Magic iMovie" where you just plug in a video camera, and the program takes all the clips, adds transitions and a soundtrack, and exports it as a DVD. It also adds more powerful effects, like Crystallize, Ripple, and Glass Distort, for starters. Also, it allows you to import non-DV video, like MP4, into your iMovie project.