Saber is used when we know something by heart.
Yo sé la fecha.
I know the date.
Mi primo todavía no sabe contar a diez.
My cousin doesn't know how to count to ten yet.

Saber is used when we know how to do something.
Mi amiga sabe patinar.
My friend knows how to skate.
Ella sabe hacer un pastel.
She knows how to make a cake.

Saber is used when we know certain facts.

Sabemos que es una clase de inglés y que se reúne los lunes y miércoles.
We know it's an English class and they meet Mondays and Wednesdays.
Sabía que habían robado el coche.
I knew they had stolen the car.