Pregame analysis is an analysis we make before the game starts, and it takes into consideration the expectations we have about the game based on several variables. Some of the important variables are available players to consider all players expect injured and suspended ones, when and where the game is played. And wait game is tougher than a home one. A gameplay than a busy schedule. For example, three games a week will differ by so much than a gameplay than a normal schedule one game a week. Lower high tempo, fast or slow rhythm Bresson rotation.
All of these variables will change, openness, goals and situation. Playing guess the top three teams in the table isn't as playing against the bottom table teams. A physical team plays differently than a technical one. Some teams like to keep possession. Some prefer counters, counter attacks, other ones genuinely adapt to the optimum scheme. The team's goals and situation, a team could sacrifice a league game by playing with the least effort and preparation to be totally ready for the game.
A post game analysis is an analysis made after the game finished, which takes in consideration what happened during the game, how a team acted and how the other one reacted. The impactful decisions during the game substitutions player position change, changing the way of play, etc. The analysis of what was right from both teams analysis who fought was wrong from both teams. The post game analysis is the most used way of analysis, as it is easier and more accurate than the pregame one. Starting in football answers, you should focus mostly if not only on the postgame analysis. There is an analysis during the game, but it requires a high and deep level of football understanding.
It is mostly made by coaches and technical staff during games. To find what is going wrong and try to solve it