Having sequential orgasms means climaxing several times, without much time in between.
For girls it’s possible to climax over and over again, without much time in between. For men this is hard to do. In their teens guys can sometimes climax two or three times in a row. But when they get older they often need a rest period before they can get a hard on for a second time.
Some guys try to be multi orgasmic by climaxing without ejaculating. This asks for special techniques, like the finger lock and redirecting energy through a specific kind of breathing.
Girls often stop masturbating after their first orgasm, because the clitoris is too sensitive to touch. But if you wait a (few) minute(s) the hypersensitivity will disappear and you can go on. Because women don’t loose all arousal after coming, many can climax again a short time after their first orgasm. This way you can have a second, third or eighth orgasm within minutes.
Being capable of many orgasms is not the same as wanting them. Some women need more than one orgasm to feel fully satiated, while others feel completely satisfied after a single climax.

Is there a difference between multiple and sequential orgasms?