Short answers, pulled from the story.
Æsir (Old Norse plural of áss) refers to gods in Germanic paganism, and can mean either the gods in general or specifically one of the two main divine families, in contrast to the Vanir. The Proto-Germanic root ansuz is typically derived from Proto-Indo-European *h₂ems-u-, related to words meaning "god" or "lord" in Sanskrit and Avestan.
The Æsir and the Vanir are two divine families who fought a war, ending in a hostage exchange: Hœnir and Mímir from the Æsir, and Njörðr, Freyr, and Kvasir from the Vanir. After the war the Vanir were increasingly counted among the Æsir, and in some poetic sources the terms overlap. Some scholars associate the Vanir with fertility and cultivation and the Æsir with power and war, though this division is disputed.
Gylfaginning lists the male Æsir as Odin, Thor, Njörðr, Freyr, Týr, Heimdallr, Bragi, Víðarr, Váli, Ullr, Forseti, and Loki. The female Æsir (ásynjur) named there include Frigg, Sága, Eir, Gefjon, Fulla, Freyja, Sjöfn, Lofn, Vár, Vör, Syn, Hlín, Snotra, Gná, Sól, and Bil. The þulur adds further ásynjur including Skaði, Sigyn, Iðunn, Nanna, and Rán.
The Swedish word åska, meaning "thunderstorm," descends from the earlier form åsekja, meaning "the driving of the áss," itself derived from the reconstructed Old East Norse ās-ækia. The name reflects the belief that thunderstorms were caused by Thor riding across the sky.
Ásatrú, meaning "faith in the Æsir," is a modern religious movement that reconstructs and practices Germanic paganism, also known as Heathenry. As of 2007, it is officially recognized by the governments of Denmark, Iceland, Norway, and Sweden. In the United Kingdom, Asatru UK is registered as a community interest company for religious activities.
An inscription on a buckle found at Vimose, dated to around 200 CE, reads a(n)sau wīja, meaning "I dedicate this to the Æsir." This is one of the earliest attested uses of the Proto-Germanic root ansuz in reference to these gods.