The below description is taken from LEGO.com.
As the world’s premier intelligence agency, the ranks of S.H.I.E.L.D. are populated by members from all walks of life. What each agent shares in common is a devotion to seeing the world kept safe from harm. Members of S.H.I.E.L.D. exemplify the best of the best, and are some of the most highly trained individuals on the planet.