When purchasing a video camera or choosing your project settings in your editing software you may come across the dimensions followed by an i or a p for example 1080i or 1080p. This stands for interlaced and progressive scan.
The difference between the two are as follows. If you imagine you video is built like a brick wall, in layers known as fields. In an interlaced video each field is offset not dissimilar to the brick wall. You have probably noticed this during moments of fast motion where you see lines like a comb at the edge of the moving subject.
Interlaced video should be deinterlaced for your final product. In Final Cut this is done by applying a deinterlace effect, in premiere pro it can be done as your send your media to Adobe Media Encoder.
Progressive scan video already has the fields aligned resulting in a much crisper image and less things to think about at edit. Be sure if you are working with progressive video not to deinterlace your video when you export it. It will reduce the quality.
If you wish your final video to be displayed on a computer monitor then always deinterlace your video or use Progressive.
You can also De interlace video in Quicktime Pro, Window > Show Movie Properties > Video Track > Deinterlace
