"Rec league" is short for "recreational league" and refers to play within a local league formed of teams from the same neighborhood or general area. A "rec team" is formed from players from the same league, and a rec team plays teams from the same league and/or surrounding leagues.
WUSA plays under the auspices of the ASA (Amatuer Softball Association), which is the oldest and largest national softball governing body. Unlike Little League Baseball, ASA does not have strict boundaries between leagues.
"All-Star" or "Tournament" teams are formed from recreational leagues according the league's selection policies. All-star/tournament teams play in various tournaments including ASA national qualifiers leading to ASA National Championship play (10U and up). All-star/tournament teams generally play in ASA Class "B". Softball is loosely structured, so All-Star/tournament teams can and do play in USSSA, USFA, NSA, etc. tournaments if they choose to enter.
"Select" teams are typically privately managed, year-round organizations formed from open tryouts or direct recruitment outside of league play. They may be part of organization that fields several select teams, they may be sponsored by a league (Deer Park, Sugar Land and Spring-Klein sponsor Select Teams, for example), or they may just be an individual team formed by a group of parents. Select teams generally play in ASA Class "A" tournaments as well as tournaments sponsored by other organizations such as USSSA, USFA, NSA, etc. Some highly successful select teams at older age groups are financed by softball equipment manufacturers.