Intelligence communities are split on whether Israel will carry out any form of strike against Iran. The facilities in question are likely to be non-civilian targets, and would, if executed, target Iran's nuclear weapons program and/or other aspects of their military.

Definitions:
Retaliatory strike - Any strike by Israel on Iranian territory (strikes on Iranian proxy groups not included).

Nuclear facilities - Any facility speculated to be doing research on nuclear weapons or nuclear technology, even if it is non-military.
1st of June in the GMT time zone.

See similar question for May 1st: