Humans (Homo sapiens) are the intelligent inhabitants of Earth. The races of the Nine Realms refer to Humans as Mortals, while the various extraterrestrial cultures living beyond the realms use the term Terrans.
Information in Timeline.
Having very limited space-faring capabilities, humans are not well known across the galaxy nor the other Realms. They have a common appearance, most similar to Asgardians and Xandarians but with the same anatomical features of the many other humanoid races. Their biology is considered "simple" by the Kree, is markedly different from Asgardians, and similar enough to be sexually compatible with Krylorians. They have short lifespans compared to certain races such as the Kree, Asgardians, Jotuns, and Celestials, and thus are often referred to as "mortal." While humans are outclassed in terms of physical ability such as strength, speed, and reflexes by races such as Asgardians and Jotuns, they are largely on par with races such as Xandarians, Krylorians, Centaurians, Chitauri, and Dark Elves. However, highly trained human fighters (such as S.H.I.E.L.D. agents) have been observed to defeat Kree on multiple occasions.
Humans are also seen to not have the biological fortitude to wield the Infinity Stones, as do Dark Elves, Celestials, Titans and Kree. However, two human beings were able to concurrently use the power of the Infinity Stones, a feat which only Thanos had displayed before. Bruce Banner used the Nano Gauntlet to resurrect everyone killed in the Snap, although using the Infinity Stones had damaged his arm. Through the use of his suit, Tony Stark materialized a makeshift Nano Gauntlet to utilize the near-omnipotent power of the Infinity Stones to decimate Thanos, an omnicidal galactic warlord, and all of his armies, even though using such tremendous power also fatally wounded Stark.
Human beings also make up for their lack of superhuman physical powers in terms of intelligence and adaptability. Some human beings have been enhanced through various means such as either advancement in science or through the use of the Tesseract. There are also human beings who can also utilize mystical arts to attain reality warping abilities or be exposed to some form of dimensional energy in order to attain superhuman abilities.