Simplify the following text for a Grade 6 native English-speaking person.
Original: Strike action , also called labor strike , on strike , greve ( of French : grÃ ve ) , or simply strike , is a work stoppage caused by the mass refusal of employees to work . A strike usually takes place in response to employee grievances .
Simplified: A sympathy strike is a strike that is done to support another group of workers on strike .