I’ll give you the short version.
A bunch of us play Fantasy FIRST–think fantasy football, but for each event we pick an alliance of 3 FRC teams. (Some exceptions apply, see [FF]: 2019 Season Long Fantasy FIRST for details)
After teams start playing events, some of us like to change our lineups to get better teams. So we have waiver drafts, where we can do that. (Also for teams that join an event after the event draft, but those were earlier in the year.) This is the 4th waiver, between Week 4 and Week 5.