What makes this show unique is the fact it takes place at the end of a legendary adventure, as the female elf protagonist (the latter is a rarity in anime) reflects on her experiences & memories during the decade-long journey with her closest companions.
The show is about love, regret, memories, moving forward, hatred & consequences of decisions. What I enjoyed about this anime is how each character had different perspectives—even hypocritical ones—& despite their flaws, they accomplished great things.
Another item I enjoyed about Frieren is that it is not another overpowered protagonist's show. While Frieren is powerful, she is also vulnerable (mismatches are the key to victory), as the show highlights during the numerous fantasy battles.
Many other characters in the show are fantastic, too, but it is best to discover that for yourself!
Although the show appears episodic at first, there is a clear destination in mind, & it is fun to watch Frieren & her new friends attempt to trek there on her journey.