To play any game, there are certain rules which the players need to follow to play and be a part of the game. Rules are basically the ethics of the game. In a parallel way, there are certain rules to play football which are as follows-
All teams must take the field with five players.
Mixed teams must take the field with a minimum of two female outfield players. ...
Unlimited interchange will be allowed for all matches.
Kick offs will be taken from half way.
No slide tackles.
No offside.
No throw ins.
No corners.
If the ball hits any part of the net behind the goalkeeper off a shot, keeper save or deflection, the ball automatically goes to the goalkeeper for a restart. An indirect free kick shall be awarded at the referees discretion should a player kick the ball into their own back net.
Goalkeepers can pass the ball out with their feet or throw it out with their hands
Goalkeepers cannot come outside of their goal circle at anytime
Goalkeepers may not pick the ball up if it has been passed to them from a team mate
Goalkeepers cannot kick the ball out of their hands
Goalkeepers must release the ball within 6 seconds
If a team kicks the ball out of the pitch, the match will be a restart with the goalkeeper of the opposing team
All free kicks are indirect
No pushing or grinding into the rebound boards
Serious foul play will be punishable by yellow and red cards
In the event of a penalty being awarded all penalty takers can only take one step before striking the ball

(https://nnsw.footballfives.com.au/fixtures-faqs-rules-r-regulations/rules-regulations-2/)

By obeying and sticking to these rules, the players can actually become experts in football.