The New York Islanders have until June 25th, 2019 to provide qualifying offers to their restricted free agents. The Islanders have four pending restricted free agents going into the 2019 offseason: Anthony Beauvillier, Michael Dal Colle, Josh Ho-Sang, and John Stevens.
Essentially, the qualifying offer is a CBA mechanism that allows teams to retain the negotiating right for players whose contracts have expired but are not yet allowed to hit unrestricted free agency.
By tending a qualifying offer teams keep their rights to the first refusal on any offer sheet that an RFA might get in free agency.