Short answers, pulled from the story.
The NFL All-Decade Teams are honorary rosters that recognize the best players from each decade of professional football. There is one team for every decade from the 1920s through the 2010s, giving the league ten teams in total.
Members of the Pro Football Hall of Fame selection committee choose the NFL All-Decade Teams. The same body that votes on Hall of Fame inductees is responsible for assembling each decade roster.
There are ten NFL All-Decade Teams, covering the 1920s, 1930s, 1940s, 1950s, 1960s, 1970s, 1980s, 1990s, 2000s, and 2010s.
The first NFL All-Decade Team covers the 1920s, honoring players from the earliest years of the league.
The most recent NFL All-Decade Team covers the 2010s, the last full decade for which a team has been named.
The NFL All-Decade Teams are selected by members of the Pro Football Hall of Fame selection committee, directly linking the honorary decade rosters to the institution that governs the sport's highest individual honor.