A strike package is a group of aircraft with different capabilities that are launched together to perform a single attack mission. The US Navy refers to the same concept as an alpha strike.
The term is normally applied to ground attack missions, where the strike package will include the bombers attacking the primary target, fighters to defend them from enemy aircraft, wild weasels to defend against ground based anti-aircraft, reconnaissance aircraft for pre- and post-raid analysis, and tanker aircraft to keep them all in the air. In some cases all of these roles can be carried out by a single aircraft with different warloads, but it is more common to use a variety of different aircraft, launched from different locations and times.