What are User Modes
CTFd has two kinds of "user modes", User Mode and Team Mode. User modes dictate how players register for the competition and how they're scored.
If you set your CTF to Team Mode, every team will need to choose a captain. Their captain should register a team and then share the team password with their teammates. Their teammates will then be able to use the team name and password to join the team.
All solves, submissions, awards, and hints gotten by a team member will be attributed the team as well as the individual user. To use a metaphor, in basketball when someone scores points the team gets the points, but we still record how many points the player has gotten for the team. The same is true in CTFd.
Under team mode everyone should register for their own user account. Then one person from each team (the captain) should register a team account and share the team name and password with their fellow teammates. The other members should then join the team using those credentials.
Solo individuals can still play in Team Mode but they will still need to register a team.
Under User mode, CTFd lets participants play on their own using their user account. Multiple players also share the same account to play together but solves and submissions will all be attributed to the same account instead of broken down by player.