ELO is a rating system originally developed for chess that measures the relative skill level of teams. In college football, it provides a more accurate ranking than traditional polls by empirically considering strength of schedule.
Teams start each season with ELO ratings based on their previous year's final ELO ratings, regressed 5% towards the mean of 1500. New teams or teams without history start at 1500.
This interactive chart shows how team ELO ratings changed throughout the season. You can select teams to compare their progression and see the impact of key games.