Use place value, known and derived facts to multiply and divide mentally, including multiplying by 0 and 1, dividing by 1

What this means, in plain words

Place value is the idea that a digit is worth a different amount depending on where it sits: the 4 in 40 is worth ten times the 4 in 4.

Multiplication is repeated addition of equal groups. Division shares a total into equal groups, or works out how many groups fit.