By tendering him an offer, the Pistons can now retain Stuckey if another team signs him to an offer sheet. Since Stuckey is a restricted free agent, the Pistons would have a week to match any offer from another team that Stuckey signs. Basically, if the Pistons really want to keep Stuckey, he will be back with them next season since they have the right of first refusal.
Jonas Jerebko is also a restricted free agent, and it's expected the Pistons will tender him a contract offer as well. Detroit has until June 30 to give him a qualifying offer.
The other Pistons players that are set to become free agents are unrestricted. This list includes Tayshaun Prince, Tracy McGrady, Chris Wilcox and DaJuan Summers.