Well, to describe it:
It's a world were fairy tales cannot be written off as just "tales" - they might be (embellished) retellings of historical events. Kinda like a Hollywood take on some historical event - because Elves, Dwarves, magic, monsters, wizards and sorcerors, they all exist. but of course, historical event rarely fit neither in a 90 minute movie nor a 5 minute Bard's ballad and wouldn't always be satisfying entertainment if told accurately.
The main characters is a "Witcher", a human altered with magic to be able to combat monsters that could easily beat a normal warrior, a sorceress from humble beginnings that doesn't have come to terms with what she sacrificed to gain her power and beauty, and a royal child with some inborn magic ability that she hasn't even fully figured.
The first season shows some important scenes of their life, each character's story told at a different speed through their life, all stories moving towards the "present", and occassionally showing where their paths crossed.
It is relatively episodic compared to many streaming shows, though there are some shared threads that tie things together and become clearer the closer you get toward the end of the season.