Every session you finish moves one number: your rating points. That number decides your tier, and your tier is what other players see next to your name. It is the same number whether you played a club night or a tournament — nothing about the setting changes what a result is worth.
The more players in the session, the more points are on the table that night. Winning among twelve is worth more than winning among four.
First place takes the biggest share and every place below it takes a steadily smaller one. Everyone who plays gets a turn-up bonus.
Last place loses what first place gained in the same session, so two accounts cannot arrange a result that lifts them both. If the bottom finisher is a guest without an account, the penalty lands on the lowest-placed real account instead.
You earn EXP for playing a round and more for winning it, then a bonus again for finishing a session. EXP is never taken away, so your level only goes up.
Your tier answers how good you are right now, so it moves in both directions. Your level answers how much you have played. Both sit on your profile, and neither one touches the other.