Loki uses his scepter to take control of Erik Selvig and Clint Barton. The film does not say what powers it; Avengers: Age of Ultron (2015) shows the Mind Stone inside.
Steve takes the 2012 scepter, with the Mind Stone in it, from Hydra sleeper agents inside S.H.I.E.L.D., and later uses it to knock out his 2012 self.
The mind-control weapon from 2012 becomes one of the six Stones the team needs.
Source: Wikipedia: Infinity Stones