i can explain for u real quick ill try my best to not make it confusing.
so genshin has a pity system and the way it works is when you pull for character's in the banners,
by every 90 wishes you'll get a confirmed 5 star character, you can pull a 5 star before that 90th wish but it's if you hadnt gotten a 5 star yet by your 89th wish, you WILL get it on your 90th. and say you pull your 5 star any time before that 90th wish, the counter resets back to zero.
so for their limited event 5 star banners, you have your character thats running in the banner for a limited amount of time (around 20 days or so) before their gone until their next return which could be months (or over a year rip shenhe....) BUT when you're pulling for them, your first 5 star pull will be a 50/50. you can either win the 50/50 and get that limited event character OR if you lose the 50/50, you get one of the standard 5 star characters that are available in the game all the time (the characters in my 2nd post of this thread)
if you lose the 50/50, your next 5 star character pull
will be the event character and it can carry over to the next banner so you don't have to worry about your wish counter reseting

. and then after you get your confirmed limited 5 star, the count resets back to zero and the next is your 50/50 again and the cycle continues lol
i hope dis made sense