They are a parody of modern life through the lens of fantastical places, characters, and events that occur on the discworld. It’s a flat land supported by 4 elephants sitting on the back of a space turtle.
There are several mini series within the collection that feature recurring characters and different story archetypes. There are the witches, a coven of 3 witches who tend to be helpful even if they don’t want to be. The night watch features Sam Vimes and other policemen of the major city of discworld who stumble through investigations. Deaths daughter features a girl who was adopted and raised by the personification of death, tall guy, kinda skinny, TALKS LIKE THIS. And the wizards college where magic is studied and knowledge is collected but rarely used.
Aside from those mini series there are lots of stand alone stories and even the books in the mini series can be read as standalone. There is no right or wrong place to start but there are some recommended reading orders that can help you decide where you want to dive in.
I may have some stuff omitted or incorrect. It has been a while since I have read the books but they maintain their position at the front and center of my bookshelf.
Equal parts timeless social commentary, fantasy, and comedy. Not too grim, not too saccharine—always juggling the big existential questions, highjinks, and word-play it'll take multiple re-reads to catch. The personification of Death is a cat lady skeleton.
It's a special experience. Others have gone over the broad strokes, so I'll instead describe my two favourite characters in the entirety of fiction.
Sam Vimes is a pragmatic, down to earth everyman. In a world full of crime, racism, magic, and political shenanigans, he tries (and mostly succeeds) to be true to his beliefs and convictions. Convictions like female dwarves deserve to identify as female if they want to, no matter how much dwarven society despises any dwarf not sticking to male identities. That anyone and everyone deserves to be hired and promoted on merit, no matter the stigma around ghouls, zombies and werewolves. He cares about his people and his city, and really tries. He may not fully understand your culture or religion, but he will defend your right to it to the death.
Rincewind is the opposite of the hero archetype. He's the coward with a thousand backs. A failed wizard, because the immensely powerful spell living in his head scares off all the other spells, all he wants is to live a nice, calm, peaceful life. Against his will, he's dragged from adventure to adventure and runs away from every exciting and mystical thing in the world. He's seen everything, done everything, and never wanted to step out of the Unseen University.