Genshin Impact uses a rarity system, where characters and weapons are separated by two tiers—Four-Star and Five-Star. This means that Five-Star is the best the game has to offer and the hardest to acquire when Four-Star is the second-highest rarity and is a tad bit easier to obtain.
Due to the gacha system, the odds of getting a Five-Star are incredibly low when compared to getting a Four-Star. This is where the game's pity system falls into play, so you don't get overwhelmingly unlucky constantly.
MiHoYo's pity system comes into place to ensure players will not get anything all the time. It's a failsafe. The system guarantees that a drop will be occur based on the number of pulls you've attempted. The game will make sure that your luck will turn around at some point or another.
A Five-Star drop will be granted after 90 wishes have been made—this is without receiving a single Five-Star character or item. If a Four-Star drop hasn't appeared after 10 wishes, one is 100 percent guaranteed to drop with the next one. If you are pulling for a weapon, the numbers are slightly different, with 80 being the pity cap for a Five-Star weapon and 10 for a Four-Star.
Though the pity system does guarantee a drop will happen, it doesn't carry anything over. Meaning if you get a Five-Star drop in that 90 wish usage, the counter resets back up to 90. The same goes for the Four-Star counter. It will not carry over the number of previously unsuccessful attempts—the pity system is no more than a failsafe to make sure you acquire something so you don't feel swindled.
Most gamers will not even know if the Pity System has even triggered, as it happens in the background. Unless you keep tabs on how many pulls you are making, you'll most likely be unaware that the pity system has been activated.
We have a whole bunch of more guides on starting you out in this new game in our Genshin Impact section!