Reason about the location of any three-digit number in the linear number system, including identifying the previous and next multiple of 100 and 10

What this means, in plain words

A multiple of a number is what you get when you multiply it by a whole number, so 12 is a multiple of 3.

A number line puts numbers in order along a line, evenly spaced, so larger and smaller can be seen rather than worked out.

A digit is one of the ten symbols, 0 to 9, that all numbers are written with.