what is prefect trial?

Hello! I'm new to this game, what is perfect trial? If anyone could please explain it to me I'd very much appreciate it!! ヽ(´▽｀；)/♪

In ppd there's an option to enable perfect trial in the song select screen and you pay a certain amount of PPDY (ppds gacha currency thing) and if you perfect a chart with it enabled you get a bonus amount of PPDY along with your icon appearing above the review section of that charts leaderboards but if you don't perfect the chart with perfect trial enabled you lose the PPDY that you initially used to start the perfect trial. There's also a leaderboard for total perfect trials.