1080i, 1080p, and 4K HD are all different types of high definition video resolutions. 1080i stands for interlaced scan, which means that the video is displayed by alternately lighting up odd and even pixel rows. In other words, the 540 odd rows are shown in one frame, followed by the 540 even rows in the next frame. 1080p, on the other hand, is a frame-based or progressive scan video, where you are dealing with frames, expressed in frames per second (fps). 1080p has a higher frame rate than 1080i, which results in a smoother and more detailed video image. 4K HD, also known as UHD, has a resolution of 3840 horizontal pixels and 2160 vertical pixels, which is four times the resolution of 1080p. This means that 4K HD has a much sharper and more detailed picture compared to 1080p and 1080i.