位取り（くらい）

Reading from the right, we have the ones, the tens, and the hundreds. The ones place is just that many; the tens place counts groups of $10$; the hundreds place counts groups of $100$. So a $7$ in the tens place means $70$, and a $7$ in the hundreds place means $700$.

If we split $342$ by place, the $3$ is in the hundreds, so it means $300$; the $4$ is in the tens, so it means $40$; and the $2$ is in the ones, so it means $2$. Adding them back gives $300+40+2=342$. Breaking a number up like this is called expanding it by place value.

To compare numbers, look at the biggest place first. For $523$ and $498$, the hundreds digits are $5$ and $4$. Since $5>4$, we know $523$ is larger. If the hundreds are the same, move on to the tens, and then to the ones.

In the Cambridge Primary Mathematics (0096) learning objectives, Stage 2 covers place value in 2-digit numbers (tens and ones), recognising zero as a place holder (2Np.01–2Np.03). Splitting up and comparing 3-digit numbers with hundreds, tens and ones comes in Stage 3 (3Np.01, 3Np.03, 3Np.04). The examples on this page use 3-digit numbers, so they match Stage 3.