system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: The difference between 720i to 720p, 1080i to 1080P?
gpt
720i first of all never existed.

The i and p stands for interlaced (i) and progressive (p) scans.  The interlaced scan does every other line on one frame then goes back and does the opposite set of lines on the next, progressive starts at pixel lines 1 and goes through to the last pixel line before going back to the beginning.

The difference is the amount of information being generated by the TV each frame, a progressive frame rate is a much larger amount of data, thus the reason why most networks use 720p/1080i, because this is the same amount of data being broadcast, it's just being displayed differently.