They use textbooks, schedules, and grades. Many of these families closely follow a scope of sequence, a list of who learns what when. Others love the interdisciplinary nature of unit studies. Still other homeschooling families prefer child-led learning, also called unschooling. They encourage their kids to follow their interests.
Cooking is home economics and math.
Watching a PBS documentary is history. Raising turkeys for 4-H is science and math. Self-selected reading and emailing friends is language arts. Designing a WEB page is computer science. And so on.