Short answers, pulled from the story.
Thor was created by writer Stan Lee, artist Jack Kirby, and scripter Larry Lieber. The character first appeared in Journey into Mystery #83 in 1962. Lee conceived the idea, drafted an outline, and assigned the scripting to his brother Lieber and the penciling to Kirby.
Mjolnir is crafted from a fictional metal called uru, which makes the hammer nearly indestructible. It is enchanted so that only those deemed worthy may lift it, and it always returns to its wielder when thrown.
Thor's arch-nemesis is his adoptive brother Loki. Loki envies Thor as heir to Asgard's throne and repeatedly plots to seize power over Asgard for himself.
Jane Foster, Beta Ray Bill, Eric Masterson, Volstagg, and Storm have all carried the title of Thor in Marvel Comics. Jane Foster became Thor during the 2014 Original Sin story arc, with the original Thor referred to as The Odinson during that period.
Chris Hemsworth portrays Thor in the Marvel Cinematic Universe, first appearing in Thor (2011). He has reprised the role across numerous films including The Avengers (2012), Thor: Ragnarok (2017), Avengers: Infinity War (2018), Avengers: Endgame (2019), and Thor: Love and Thunder (2022).
Donald Blake was Thor's original human alter ego, a surgeon who could transform into Thor by striking a walking stick on the ground. In Thor #159 (1968), it was revealed that Blake was a fabricated identity created by Odin to teach Thor humility, and that Thor was the actual mythological god all along.